Subject To Completion, dated March 10, 2016

PRICING SUPPLEMENT No. 637 dated March     , 2016

(To Product Supplement No. 1 dated March 18, 2015,

Market Measure Supplement dated March 18, 2015,

Prospectus Supplement dated March 18, 2015

and Prospectus dated March 18, 2015)

Wells Fargo & Company

Medium-Term Notes, Series K

Equity Index Linked Securities

Market Linked Securities—Leveraged Upside Participation
to a Cap and Fixed Percentage Buffered Downside

Principal at Risk Securities Linked to the S&P 500^® Index due September 18, 2018

n

Linked to the S&P 500^® Index

n

Unlike ordinary debt securities, the securities do not pay interest or repay a fixed amount of principal at maturity. Instead, the securities provide for a payment at maturity that may be greater than, equal to or less than the original offering price of the securities, depending on the performance of the Index from its starting level to its ending level. The payment at maturity will reflect the following terms:

n

If the level of the Index increases, you will receive the original offering price plus 125% participation in the upside performance of the Index, subject to a maximum total return at maturity of 40.00% to 45.00% (to be determined on the pricing date) of the original offering price

n

If the level of the Index decreases but the decrease is not more than 10%, you will be repaid the original offering price

n

If the level of the Index decreases by more than 10%, you will receive less than the original offering price and have 1-to-1 downside exposure to the decrease in the level of the Index in excess of 10%

n

Investors may lose up to 90% of the original offering price

n

All payments on the securities are subject to the credit risk of Wells Fargo & Company, and you will have no ability to pursue any securities included in the Index for payment; if Wells Fargo & Company defaults on its obligations, you could lose some or all of your investment

n

No periodic interest payments or dividends

n

No exchange listing; designed to be held to maturity

Wells Fargo Securities, LLC, a wholly owned subsidiary of Wells Fargo & Company, is the agent for the distribution of the securities and is acting as principal. See “Investment Description” in this pricing supplement for further information.

the possibility of a leveraged return at maturity if the level of the Index increases from its starting level to its ending level, provided that the total return at maturity of the securities will not exceed the maximum total return of 40.00% to 45.00% of the original offering price, as determined on the pricing date;

repayment of principal if, and only if, the ending level of the Index is not less than the starting level by more than 10%; and

exposure to decreases in the level of the Index if and to the extent the ending level is less than the starting level by more than 10%.

Product Supplement No. 1 dated March 18, 2015 filed with the SEC on March  18, 2015:
http://www.sec.gov/Archives/edgar/data/72971/000119312515096492/d890820d424b2.htm

Market Measure Supplement dated March 18, 2015 filed with the SEC on March  18, 2015:
http://www.sec.gov/Archives/edgar/data/72971/000119312515096591/d890724d424b2.htm

Prospectus Supplement dated March 18, 2015 and Prospectus dated March 18, 2015 filed with the SEC on March  18, 2015:
http://www.sec.gov/Archives/edgar/data/72971/000119312515096449/d890684d424b2.htm

seek 125% leveraged exposure to the upside performance of the Index if the ending level is greater than the starting level, subject to the maximum total return at maturity of 40.00% to 45.00% (to be determined on the pricing date) of the original offering price;

desire to limit downside exposure to the Index through the 10% buffer;

understand that if the ending level is less than the starting level by more than 10%, they will receive less, and possibly 90% less, than the original offering price per security at maturity;

are willing to forgo interest payments on the securities and dividends on securities included in the Index; and

are willing to hold the securities until maturity.

seek a liquid investment or are unable or unwilling to hold the securities to maturity;

are unwilling to accept the risk that the ending level of the Index may decrease by more than 10% from the starting level;

seek uncapped exposure to the upside performance of the Index;

seek full return of the original offering price of the securities at stated maturity;

are unwilling to purchase securities with an estimated value as of the pricing date that is lower than the original offering price and that may be as low as the lower estimated value set forth on the cover page;

seek current income;

are unwilling to accept the risk of exposure to the large capitalization segment of the United States equity market;

seek exposure to the Index but are unwilling to accept the risk/return trade-offs inherent in the payment at stated maturity for the securities;

are unwilling to accept the credit risk of Wells Fargo to obtain exposure to the Index generally, or to the exposure to the Index that the securities provide specifically; or

prefer the lower risk of fixed income investments with comparable maturities issued by companies with comparable credit ratings.

  Market Measure:

S&P 500^® Index

  Pricing Date:

March 15, 2016*

  Issue Date:

March 18, 2016* (T+3)

  Original Offering

  Price:

$1,000 per security. References in this pricing supplement to a “security” are to a security with a face amount of $1,000.

  Redemption

  Amount:

The “redemption amount” per security will equal:

•

if the ending level is greater than the starting level: the lesser of:

(i)    $1,000 plus:

(ii)    the capped value;

•

if the ending level is less than or equal to the starting level, but greater than or equal to the threshold level: $1,000; or

•

if the ending level is less than the threshold level: $1,000 minus:

If the ending level is less than the threshold level, you will receive less, and possibly 90% less, than the original offering price of your securities at maturity.

  Stated Maturity

  Date:

September 18, 2018*. If the calculation day is postponed, the stated maturity date will be postponed to the later of (i) September 18, 2018* and (ii) the third business day after the calculation day as postponed.

  Starting Level:

            , the closing level of the Index on the pricing date.

  Ending Level:

The “ending level” will be the closing level of the Index on the calculation day.

The “capped value” will be determined on the pricing date and will be within the range of 140.00% to 145.00% of the original offering price per security ($1,400.00 to $1,450.00 per security). As a result of the capped value, the maximum total return at maturity of the securities will be 40.00% to 45.00% of the original offering price.

  Threshold Level:

            , which is equal to 90% of the starting level.

  Participation Rate:

125%

September 13, 2018*. If such day is not a trading day, the calculation day will be postponed to the next succeeding trading day. The calculation day is also subject to postponement due to the occurrence of a market disruption event.

  Calculation Agent:

Wells Fargo Securities, LLC

For a discussion of the material U.S. federal income tax consequences of the ownership and disposition of the securities, see “United States Federal Tax Considerations.”

To the extent that we make any change to the expected pricing date or expected issue date, the calculation day and stated maturity date may also be changed in our discretion to ensure that the term of the securities remains the same.

Wells Fargo Securities, LLC, a wholly owned subsidiary of Wells Fargo & Company. The agent may resell the securities to other securities dealers at the original offering price of the securities.

The agent or another affiliate of ours expects to realize hedging profits projected by its proprietary pricing models to the extent it assumes the risks inherent in hedging our obligations under the securities. If any dealer participating in the distribution of the securities or any of its affiliates conducts hedging activities for us in connection with the securities, that dealer or its affiliate will expect to realize a profit projected by its proprietary pricing models from such hedging activities. Any such projected profit will be in addition to the discount or concession received in connection with the sale of the securities to you.

  Denominations:

$1,000 and any integral multiple of $1,000.

94986RH61

If The Ending Level Is Less Than The Threshold Level, You Will Receive Less, And Possibly 90% Less, Than The Original Offering Price Of Your Securities At Maturity. If the ending level is less than the threshold level, the redemption amount that you receive at stated maturity will be reduced by an amount equal to the decline in the level of the Index to the extent it is below the threshold level (expressed as a percentage of the starting level). The threshold level is 90% of the starting level. As a result, you may receive less, and possibly 90% less, than the original offering price per security at maturity even if the level of the Index is greater than or equal to the starting level or the threshold level at certain times during the term of the securities.

No Periodic Interest Will Be Paid On The Securities. No periodic payments of interest will be made on the securities. However, if the agreed-upon tax treatment is successfully challenged by the Internal Revenue Service (the “IRS”), you may be required to recognize taxable income over the term of the securities. You should review the sections of this pricing supplement and the accompanying product supplement entitled “United States Federal Tax Considerations.”

Your Return Will Be Limited By The Capped Value And May Be Lower Than The Return On A Direct Investment In The Index. The opportunity to participate in the possible increases in the level of the Index through an investment in the securities will be limited because the redemption amount will not exceed the capped value. Furthermore, the effect of the participation rate will be progressively reduced for all ending levels exceeding the ending level at which the capped value is reached.

The Securities Are Subject To The Credit Risk Of Wells Fargo. The securities are our obligations and are not, either directly or indirectly, an obligation of any third party. Any amounts payable under the securities are subject to our creditworthiness, and you will have no ability to pursue any securities included in the Index for payment. As a result, our actual and perceived creditworthiness may affect the value of the securities and, in the event we were to default on our obligations, you may not receive any amounts owed to you under the terms of the securities.

The Estimated Value Of The Securities On The Pricing Date, Based On WFS’s Proprietary Pricing Models, Will Be Less Than The Original Offering Price. The original offering price of the securities includes certain costs that are borne by you. Because of these costs, the estimated value of the securities on the pricing date will be less than the original offering price. The costs included in the original offering price relate to selling, structuring, hedging and issuing the securities, as well as to our funding considerations for debt of this type. The costs related to selling, structuring, hedging and issuing the securities include (i) the agent discount (if any), (ii) the projected profit that our hedge counterparty (which may be one of our affiliates) expects to realize for assuming risks inherent in hedging our obligations under the securities and (iii) hedging and other costs relating to the offering of the securities. Our funding considerations are reflected in the fact that we determine the economic terms of the securities based on an assumed funding rate that is generally lower than our secondary market rates. If the costs relating to selling, structuring, hedging and issuing the securities were lower, or if the assumed funding rate we use to determine the economic terms of the securities were higher, the economic terms of the securities would be more favorable to you and the estimated value would be higher.

The Estimated Value Of The Securities Is Determined By Our Affiliate’s Pricing Models, Which May Differ From Those Of Other Dealers. The estimated value of the securities was determined for us by WFS using its proprietary pricing models and related market inputs and assumptions referred to above under “Investment Description—Determining the estimated value.” Certain inputs to these models may be determined by WFS in its discretion. WFS’s views on these inputs may differ from other dealers’ views, and WFS’s estimated value of the securities may be higher, and perhaps materially higher, than the estimated value of the securities that would be determined by other dealers in the market. WFS’s models and its inputs and related assumptions may prove to be wrong and therefore not an accurate reflection of the value of the securities.

The Estimated Value Of The Securities Is Not An Indication Of The Price, If Any, At Which WFS Or Any Other Person May Be Willing To Buy The Securities From You In The Secondary Market. The price, if any, at which WFS or any of its affiliates may purchase the securities in the secondary market will be based on WFS’s proprietary pricing models and will fluctuate over the term of the securities as a result of changes in the market and other factors described in the next risk consideration. Any such secondary market price for the securities will also be reduced by a bid-offer spread, which may vary depending on the aggregate face amount of the securities to be purchased in the secondary market transaction, and the expected cost of unwinding any related hedging transactions. Unless the factors described in the next risk consideration change significantly in your favor, any such secondary market price for the securities is likely to be less than the original offering price.

The Value Of The Securities Prior To Stated Maturity Will Be Affected By Numerous Factors, Some Of Which Are Related In Complex Ways. The value of the securities prior to stated maturity will be affected by the level of the Index at that time, interest rates at that time and a number of other factors, some of which are interrelated in complex ways. The effect of any one factor may be offset or magnified by the effect of another factor. The following factors, which we refer to as the “derivative component factors,” are expected to affect the value of the securities: Index performance; interest rates; volatility of the Index; time remaining to maturity; and dividend yields on the securities included in the Index. In addition to the derivative component factors, the value of the securities will be affected by actual or anticipated changes in our creditworthiness, as reflected in our secondary market rates. Because numerous factors are expected to affect the value of the securities, changes in the level of the Index may not result in a comparable change in the value of the securities.

The Securities Will Not Be Listed On Any Securities Exchange And We Do Not Expect A Trading Market For The Securities To Develop. The securities will not be listed or displayed on any securities exchange or any automated quotation system. Although the agent and/or its affiliates may purchase the securities from holders, they are not obligated to do so and are not required to make a market for the securities. There can be no assurance that a secondary market will develop. Because we do not expect that any market makers will participate in a secondary market for the securities, the price at which you may be able to sell your securities is likely to depend on the price, if any, at which the agent is willing to buy your securities. If a secondary market does exist, it may be limited. Accordingly, there may be a limited number of buyers if you decide to sell your securities prior to stated maturity. This may affect the price you receive upon such sale. Consequently, you should be willing to hold the securities to stated maturity.

The Amount You Receive On The Securities Will Depend Upon The Performance Of The Index And Therefore The Securities Are Subject To The Following Risks, As Discussed In More Detail In The Product Supplement:

Your Return On The Securities Could Be Less Than If You Owned Securities Included In The Index. Your return on the securities will not reflect the return you would realize if you actually owned the securities included in the Index because, among other reasons, the redemption amount will be determined by reference to the ending level of the Index, which will be calculated by reference to the prices of the securities in the Index without taking into consideration the value of dividends paid on those securities. In addition, the redemption amount will not be greater than the capped value.

Historical Levels Of The Index Should Not Be Taken As An Indication Of The Future Performance Of The Index During The Term Of The Securities.

Changes That Affect The Index May Adversely Affect The Value Of The Securities And The Amount You Will Receive At Stated Maturity.

We Cannot Control Actions By Any Of The Unaffiliated Companies Whose Securities Are Included In The Index.

We And Our Affiliates Have No Affiliation With The Index Sponsor And Have Not Independently Verified Its Public Disclosure Of Information.

The Stated Maturity Date May Be Postponed If The Calculation Day Is Postponed. The calculation day will be postponed if the originally scheduled calculation day is not a trading day or if the calculation agent determines that a market disruption event has occurred or is continuing on the calculation day. If such a postponement occurs, the stated maturity date will be the later of (i) the initial stated maturity date and (ii) three business days after the postponed calculation day.

Our Economic Interests And Those Of Any Dealer Participating In The Offering Are Potentially Adverse To Your Interests. You should be aware of the following ways in which our economic interests and those of any dealer participating in the distribution of the securities, which we refer to as a “participating dealer,” are potentially adverse to your interests as an investor in the securities. In engaging in certain of the activities described below, our affiliates or any participating dealer or its affiliates may take actions that may adversely affect the value of and your return on the securities, and in so doing they will have no obligation to consider your interests as an investor in the securities. Our affiliates or any participating dealer or its affiliates may realize a profit from these activities even if investors do not receive a favorable investment return on the securities.

The calculation agent is our affiliate and may be required to make discretionary judgments that affect the return you receive on the securities. WFS, which is our affiliate, will be the calculation agent for the securities. As calculation agent, WFS will determine the ending level of the Index and may be required to make other determinations that affect the return you receive on the securities at maturity. In making these determinations, the calculation agent may be required to make discretionary judgments, including determining whether a market disruption event has occurred on the scheduled calculation day, which may result in postponement of the calculation day; determining the ending level of the Index if the calculation day is postponed to the last day to which it may be postponed and a market disruption event occurs on that day; if the Index is discontinued, selecting a successor index or, if no successor index is available, determining the ending level of the Index; and determining whether to adjust the ending level of the Index on the calculation day in the event of certain changes in or modifications to the Index. In making these discretionary judgments, the fact that WFS is our affiliate may cause it to have economic interests that are adverse to your interests as an investor in the securities, and WFS’s determinations as calculation agent may adversely affect your return on the securities.

The estimated value of the securities was calculated by our affiliate and is therefore not an independent third-party valuation. WFS calculated the estimated value of the securities set forth on the cover page of this pricing supplement, which involved discretionary judgments by WFS, as described under “Selected Risk Considerations—The Estimated Value Of The Securities Is Determined By Our Affiliate’s Pricing Models, Which May Differ From Those Of Other Dealers” above. Accordingly, the estimated value of the securities set forth on the cover page of this pricing supplement is not an independent third-party valuation.

Research reports by our affiliates or any participating dealer or its affiliates may be inconsistent with an investment in the securities and may adversely affect the level of the Index. Our affiliates or any dealer participating in the offering of the securities or its affiliates may, at present or in the future, publish research reports on the Index or the companies whose securities are included in the Index. This research is modified from time to time without notice and may, at present or in the future, express opinions or provide recommendations that are inconsistent with purchasing or holding the securities. Any research reports on the Index or the companies whose securities are included in the Index could adversely affect the level of the Index and, therefore, adversely affect the value of and your return on the securities. You are encouraged to derive information concerning the Index from multiple sources and should not rely on the views expressed by us or our affiliates or any participating dealer or its affiliates. In addition, any research reports on the Index or the companies whose securities are included in the Index published on or prior to the pricing date could result in an increase in the level of the Index on the pricing date, which would adversely affect investors in the securities by increasing the level at which the Index must close on the calculation day in order for investors in the securities to receive a favorable return.

Business activities of our affiliates or any participating dealer or its affiliates with the companies whose securities are included in the Index may adversely affect the level of the Index. Our affiliates or any participating dealer or its affiliates may, at present or in the future, engage in business with the companies whose securities are included in the Index, including making loans to those companies (including exercising creditors’ remedies with respect to such loans), making equity investments in those companies or providing investment banking, asset management or other advisory services to those companies. These business activities could adversely affect the level of the Index and, therefore, adversely affect the value of and your return on the securities. In addition, in the course of these business activities, our affiliates or any participating dealer or its affiliates may acquire non-public information about one or more of the companies whose securities are included in the Index. If our affiliates or any participating dealer or its affiliates do acquire such non-public information, we and they are not obligated to disclose such non-public information to you.

Hedging activities by our affiliates or any participating dealer or its affiliates may adversely affect the level of the Index. We expect to hedge our obligations under the securities through one or more hedge counterparties, which may include our affiliates or any participating dealer or its affiliates. Pursuant to such hedging activities, our hedge counterparties may acquire securities included in the Index or listed or over-the-counter derivative or synthetic instruments related to the Index or such securities. Depending on, among other things, future market conditions, the aggregate amount and the composition of such positions are likely to vary over time. To the extent that our hedge counterparties have a long hedge position in any of the securities included in the Index, or derivative or synthetic instruments related to the Index or such securities, they may liquidate a portion of such holdings at or about the time of the calculation day or at or about the time of a change in the securities included in the Index. These hedging activities could potentially adversely affect the level of the Index and, therefore, adversely affect the value of and your return on the securities.

Trading activities by our affiliates or any participating dealer or its affiliates may adversely affect the level of the Index. Our affiliates or any participating dealer or its affiliates may engage in trading in the securities included in the Index and other instruments relating to the Index or such securities on a regular basis as part of their general broker-dealer and other businesses. Any of these trading activities could potentially adversely affect the level of the Index and, therefore, adversely affect the value of and your return on the securities.

A participating dealer or its affiliates may realize hedging profits projected by its proprietary pricing models in addition to any selling concession, creating a further incentive for the participating dealer to sell the securities to you. If any participating dealer or any of its affiliates conducts hedging activities for us in connection with the securities, that participating dealer or its affiliates will expect to realize a projected profit from such hedging activities. If a participating dealer receives a concession for the sale of the securities to you, this projected hedging profit will be in addition to the concession, creating a further incentive for the participating dealer to sell the securities to you.

The U.S. Federal Tax Consequences Of An Investment In The Securities Are Unclear. There is no direct legal authority regarding the proper U.S. federal tax treatment of the securities, and we do not plan to request a ruling from the IRS. Consequently, significant aspects of the tax treatment of the securities are uncertain, and the IRS or a court might not agree with the treatment of the securities as prepaid derivative contracts that are “open transactions” for U.S. federal income tax purposes. If the IRS were successful in asserting an alternative treatment of the securities, the tax consequences of ownership and disposition of the securities might be materially and adversely affected. In addition, in 2007 the U.S. Treasury Department and the IRS released a notice requesting comments on various issues regarding the U.S. federal income tax treatment of “prepaid forward contracts” and similar instruments. Any Treasury regulations or other guidance promulgated after consideration of these issues could materially and adversely affect the tax consequences of an investment in the securities, including the character and timing of income or loss and the degree, if any, to which income realized by non-U.S. persons should be subject to withholding tax, possibly with retroactive effect. You should read carefully the sections of this pricing supplement and the accompanying product supplement entitled “United States Federal Tax Considerations.” You should also consult your tax adviser regarding the U.S. federal tax consequences of an investment in the securities, as well as tax consequences arising under the laws of any state, local or non-U.S. taxing jurisdiction.

the hypothetical percentage change from the hypothetical starting level to the hypothetical ending level;

the hypothetical redemption amount payable at stated maturity per security;

the hypothetical total pre-tax rate of return; and

the hypothetical pre-tax annualized rate of return.

Hypothetical

ending level

Hypothetical

percentage change

from the hypothetical

starting level to the

  hypothetical ending level  

Hypothetical

  redemption amount  

payable at

stated maturity

per security

Hypothetical

pre-tax total

rate of return

Hypothetical

pre-tax

annualized

rate of return⁽¹⁾

The annualized rates of return are calculated on a semi-annual bond equivalent basis with compounding.

The hypothetical starting level. The actual starting level will be determined on the pricing date.

  x  125%  

  =  $1,062.50

  x  125%  

  =  $1,500.00

  =  $600.00

2006

First Quarter

Second Quarter

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2007

First Quarter

Second Quarter

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2008

First Quarter

Second Quarter

Third Quarter

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2009

First Quarter

Second Quarter

Third Quarter

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2010

First Quarter

Second Quarter

Third Quarter

Fourth Quarter

2011

First Quarter

Second Quarter

Third Quarter

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2012

First Quarter

Second Quarter

Third Quarter

Fourth Quarter

2013

First Quarter

Second Quarter

Third Quarter

Fourth Quarter

2014

First Quarter

Second Quarter

Third Quarter

Fourth Quarter

2015

First Quarter

Second Quarter

Third Quarter

Fourth Quarter

2016

January 1, 2016 to March 8, 2016

You should not recognize taxable income over the term of the securities prior to maturity, other than pursuant to a sale or exchange.

Upon a sale or exchange of a security (including retirement at maturity), you should recognize capital gain or loss equal to the difference between the amount realized and your tax basis in the security. Such gain or loss should be long-term capital gain or loss if you held the security for more than one year.