Primary Offering Prospectus (Form 424B2)

Callable Contingent Coupon Equity Linked Securities Linked to the Worst Performing of the Nasdaq-100 Index^®, the Russell 2000^® Index and the S&P 500^® Index Due November 25, 2026

(Key Terms continued on next page)

(1) Citigroup Global Markets Holdings Inc. currently expects that the estimated value of the securities on the pricing date will be at least $935.00 per security, which will be less than the issue price. The estimated value of the securities is based on CGMI's proprietary pricing models and our internal funding rate. It is not an indication of actual profit to CGMI or other of our affiliates, nor is it an indication of the price, if any, at which CGMI or any other person may be willing to buy the securities from you at any time after issuance. See "Valuation of the Securities" in this pricing supplement.

(2) CGMI will pay selected dealers a structuring fee of up to $3.75 for each security sold in this offering. We may also engage other firms to provide marketing or promotional services in connection with the distribution of the securities. CGMI will pay these service providers a fee of up to $3.50 per security in consideration for providing marketing, education, structuring or referral services with respect to financial advisors or selected dealers. For more information on the distribution of the securities, see "Supplemental Plan of Distribution" in this pricing supplement. CGMI and its affiliates may profit from expected hedging activity related to this offering, even if the value of the securities declines. See "Use of Proceeds and Hedging" in the accompanying prospectus.

Investing in the securities involves risks not associated with an investment in conventional debt securities. See "Summary Risk Factors" beginning on page PS-6.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities or determined that this pricing supplement and the accompanying product supplement, underlying supplement, prospectus supplement and prospectus are truthful or complete. Any representation to the contrary is a criminal offense.

You should read this pricing supplement together with the accompanying product supplement, underlying supplement, prospectus supplement and prospectus, which can be accessed via the hyperlinks below:

Product Supplement No. EA-04-10 dated March 7, 2023 Underlying Supplement No. 11 dated March 7, 2023
Prospectus Supplement and Prospectus each dated March 7, 2023

The securities are not bank deposits and are not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency, nor are they obligations of, or guaranteed by, a bank.

Additional Information

The terms of the securities are set forth in the accompanying product supplement, prospectus supplement and prospectus, as supplemented by this pricing supplement. The accompanying product supplement, prospectus supplement and prospectus contain important disclosures that are not repeated in this pricing supplement. For example, the accompanying product supplement contains important information about how the closing value of each underlying will be determined and about adjustments that may be made to the terms of the securities upon the occurrence of market disruption events and other specified events with respect to each underlying. The accompanying underlying supplement contains information about each underlying that is not repeated in this pricing supplement. It is important that you read the accompanying product supplement, underlying supplement, prospectus supplement and prospectus together with this pricing supplement before deciding whether to invest in the securities. Certain terms used but not defined in this pricing supplement are defined in the accompanying product supplement.

Hypothetical Examples

The examples in the first section below illustrate how to determine whether a contingent coupon will be paid following a valuation date. The examples in the second section below illustrate how to determine the payment at maturity on the securities, assuming the securities are not redeemed prior to maturity. The examples are solely for illustrative purposes, do not show all possible outcomes and are not a prediction of any payment that may be made on the securities.

The examples below are based on the following hypothetical values and do not reflect the actual initial underlying values, coupon barrier values or final barrier values of the underlyings. For the actual initial underlying value, coupon barrier value and final barrier value of each underlying, see the cover page of this pricing supplement. We have used these hypothetical values, rather than the actual values, to simplify the calculations and aid understanding of how the securities work. However, you should understand that the actual payments on the securities will be calculated based on the actual initial underlying value, coupon barrier value and final barrier value of each underlying, and not the hypothetical values indicated below. For ease of analysis, figures below have been rounded. The examples below assume that the contingent coupon rate is set at the lowest value indicated on the cover page of this pricing supplement. The actual contingent coupon rate will be determined on the pricing date.

Hypothetical Examples of Contingent Coupon Payments Following a Valuation Date

The three hypothetical examples below illustrate how to determine whether a contingent coupon will be paid following a hypothetical valuation date, assuming that the closing values of the underlyings on the hypothetical valuation date are as indicated below.

Example 1: On the hypothetical valuation date, the Russell 2000^® Index has the lowest underlying return and, therefore, is the worst performing underlying on the hypothetical valuation date. In this scenario, the closing value of the worst performing underlying on the hypothetical valuation date is greater than its coupon barrier value. As a result, investors in the securities would receive the contingent coupon payment on the related contingent coupon payment date.

Example 2: On the hypothetical valuation date, the Nasdaq-100 Index^® has the lowest underlying return and, therefore, is the worst performing underlying on the hypothetical valuation date. In this scenario, the closing value of the worst performing underlying on the hypothetical valuation date is less than its coupon barrier value. As a result, investors would not receive any payment on the related contingent coupon payment date.

Investors in the securities will not receive a contingent coupon on the contingent coupon payment date following a valuation date if the closing value of the worst performing underlying on that valuation date is less than its coupon barrier value. Whether a contingent coupon is paid following a valuation date depends solely on the closing value of the worst performing underlying on that valuation date.

Example 3: On the hypothetical valuation date, the S&P 500^® Index has the lowest underlying return and, therefore, is the worst performing underlying on the hypothetical valuation date. In this scenario, the closing value of the worst performing underlying on the hypothetical valuation date is less than its coupon barrier value. As a result, investors would not receive any payment on the related contingent coupon payment date.

Hypothetical Examples of the Payment at Maturity on the Securities

The next four hypothetical examples illustrate the calculation of the payment at maturity on the securities, assuming that the securities have not been earlier redeemed and that the final underlying values of the underlyings are as indicated below.

Example 4: On the final valuation date, the Nasdaq-100 Index^® has the lowest underlying return and, therefore, is the worst performing underlying on the final valuation date. In this scenario, the final underlying value of the worst performing underlying on the final valuation date is greater than its final barrier value and its coupon barrier value. Accordingly, at maturity, you would receive the stated principal amount of the securities plus the contingent coupon payment due at maturity, but you would not participate in the appreciation of any of the underlyings.

Example 5: On the final valuation date, the Russell 2000^® Index has the lowest underlying return and, therefore, is the worst performing underlying on the final valuation date. In this scenario, the final underlying value of the worst performing underlying on the final valuation date is less than its coupon barrier value but greater than its final barrier value. Accordingly, at maturity, you would receive the stated principal amount of the securities, but would not receive any contingent coupon payment at maturity.

Example 6: On the final valuation date, the S&P 500^® Index has the lowest underlying return and, therefore, is the worst performing underlying on the final valuation date. In this scenario, the final underlying value of the worst performing underlying on the final valuation date is less than its final barrier value. Accordingly, at maturity, you would receive a payment per security calculated as follows:

Payment at maturity = $1,000.00 + ($1,000.00 × the underlying return of the worst performing underlying on the final valuation date)

= $1,000.00 + ($1,000.00 × -50.00%)

= $1,000.00 + -$500.00

= $500.00

In this scenario, because the final underlying value of the worst performing underlying on the final valuation date is less than its final barrier value, you would lose a significant portion of your investment in the securities. In addition, because the final underlying value of the worst performing underlying on the final valuation date is below its coupon barrier value, you would not receive any contingent coupon payment at maturity.

Example 7: On the final valuation date, the Nasdaq-100 Index^® has the lowest underlying return and, therefore, is the worst performing underlying on the final valuation date. In this scenario, the final underlying value of the worst performing underlying on the final valuation date is less than its final barrier value. Accordingly, at maturity, you would receive a payment per security calculated as follows:

Payment at maturity = $1,000.00 + ($1,000.00 × the underlying return of the worst performing underlying on the final valuation date)

= $1,000.00 + ($1,000.00 × -80.00%)

= $1,000.00 + -$800.00

= $200.00

In this scenario, because the final underlying value of the worst performing underlying on the final valuation date is less than its final barrier value, you would lose a significant portion of your investment in the securities. In addition, because the final underlying value of the worst performing underlying on the final valuation date is below its coupon barrier value, you would not receive any contingent coupon payment at maturity.

It is possible that the closing value of the worst performing underlying will be less than its coupon barrier value on each valuation date and less than its final barrier value on the final valuation date, such that you will not receive any contingent coupon payments over the term of the securities and will receive significantly less than the stated principal amount of your securities, and possibly nothing, at maturity.

Summary Risk Factors

An investment in the securities is significantly riskier than an investment in conventional debt securities. The securities are subject to all of the risks associated with an investment in our conventional debt securities (guaranteed by Citigroup Inc.), including the risk that we and Citigroup Inc. may default on our obligations under the securities, and are also subject to risks associated with each underlying. Accordingly, the securities are suitable only for investors who are capable of understanding the complexities and risks of the securities. You should consult your own financial, tax and legal advisors as to the risks of an investment in the securities and the suitability of the securities in light of your particular circumstances.

The following is a summary of certain key risk factors for investors in the securities. You should read this summary together with the more detailed description of risks relating to an investment in the securities contained in the section "Risk Factors Relating to the Securities" beginning on page EA-7 in the accompanying product supplement. You should also carefully read the risk factors included in the accompanying prospectus supplement and in the documents incorporated by reference in the accompanying prospectus, including Citigroup Inc.'s most recent Annual Report on Form 10-K and any subsequent Quarterly Reports on Form 10-Q, which describe risks relating to the business of Citigroup Inc. more generally.

Because there is not an active market for traded instruments referencing our outstanding debt obligations, CGMI determines our secondary market rate based on the market price of traded instruments referencing the debt obligations of Citigroup Inc., our parent company and the guarantor of all payments due on the securities, but subject to adjustments that CGMI makes in its sole discretion. As a result, our secondary market rate is not a market-determined measure of our creditworthiness, but rather reflects the market's perception of our parent company's creditworthiness as adjusted for discretionary factors such as CGMI's preferences with respect to purchasing the securities prior to maturity.

Non-U.S. investors should note that persons having withholding responsibility in respect of the securities may withhold on any coupon payment paid to a non-U.S. investor, generally at a rate of 30%. To the extent that we have withholding responsibility in respect of the securities, we intend to so withhold.

You should read carefully the discussion under "United States Federal Tax Considerations" and "Risk Factors Relating to the Securities" in the accompanying product supplement and "United States Federal Tax Considerations" in this pricing supplement. 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.

Information About the Nasdaq-100 Index^®

The Nasdaq-100 Index^® is a modified market capitalization-weighted index of stocks of the 100 largest non-financial companies listed on the Nasdaq Stock Market. All stocks included in the Nasdaq-100 Index^® are traded on a major U.S. exchange. The Nasdaq-100 Index^® was developed by the Nasdaq Stock Market, Inc. and is calculated, maintained and published by Nasdaq, Inc.

Please refer to the section "Equity Index Descriptions- The Nasdaq-100 Index^®" in the accompanying underlying supplement for additional information.

We have derived all information regarding the Nasdaq-100 Index^® from publicly available information and have not independently verified any information regarding the Nasdaq-100 Index^®. This pricing supplement relates only to the securities and not to the Nasdaq-100 Index^®. We make no representation as to the performance of the Nasdaq-100 Index^® over the term of the securities.

The securities represent obligations of Citigroup Global Markets Holdings Inc. (guaranteed by Citigroup Inc.) only. The sponsor of the Nasdaq-100 Index^® is not involved in any way in this offering and has no obligation relating to the securities or to holders of the securities.

Historical Information

The closing value of the Nasdaq-100 Index^® on December 12, 2024 was 21,615.27.

The graph below shows the closing value of the Nasdaq-100 Index^® for each day such value was available from January 2, 2014 to December 12, 2024. We obtained the closing values from Bloomberg L.P., without independent verification. You should not take historical closing values as an indication of future performance.

Information About the Russell 2000^® Index

The Russell 2000^® Index is designed to track the performance of the small capitalization segment of the U.S. equity market. All stocks included in the Russell 2000^® Index are traded on a major U.S. exchange. It is calculated and maintained by FTSE Russell.

Please refer to the section "Equity Index Descriptions- The Russell Indices" in the accompanying underlying supplement for additional information.

We have derived all information regarding the Russell 2000^® Index from publicly available information and have not independently verified any information regarding the Russell 2000^® Index. This pricing supplement relates only to the securities and not to the Russell 2000^® Index. We make no representation as to the performance of the Russell 2000^® Index over the term of the securities.

The securities represent obligations of Citigroup Global Markets Holdings Inc. (guaranteed by Citigroup Inc.) only. The sponsor of the Russell 2000^® Index is not involved in any way in this offering and has no obligation relating to the securities or to holders of the securities.

Historical Information

The closing value of the Russell 2000^® Index on December 12, 2024 was 2,361.081.

The graph below shows the closing value of the Russell 2000^® Index for each day such value was available from January 2, 2014 to December 12, 2024. We obtained the closing values from Bloomberg L.P., without independent verification. You should not take historical closing values as an indication of future performance.

Information About the S&P 500^® Index

The S&P 500^® Index consists of the common stocks of 500 issuers selected to provide a performance benchmark for the large capitalization segment of the U.S. equity markets. It is calculated and maintained by S&P Dow Jones Indices LLC.

Please refer to the section "Equity Index Descriptions- The S&P U.S. Indices" in the accompanying underlying supplement for additional information.

We have derived all information regarding the S&P 500^® Index from publicly available information and have not independently verified any information regarding the S&P 500^® Index. This pricing supplement relates only to the securities and not to the S&P 500^® Index. We make no representation as to the performance of the S&P 500^® Index over the term of the securities.

The securities represent obligations of Citigroup Global Markets Holdings Inc. (guaranteed by Citigroup Inc.) only. The sponsor of the S&P 500^® Index is not involved in any way in this offering and has no obligation relating to the securities or to holders of the securities.

Historical Information

The closing value of the S&P 500^® Index on December 12, 2024 was 6,051.25.

The graph below shows the closing value of the S&P 500^® Index for each day such value was available from January 2, 2014 to December 12, 2024. We obtained the closing values from Bloomberg L.P., without independent verification. You should not take historical closing values as an indication of future performance.

United States Federal Tax Considerations

You should read carefully the discussion under "United States Federal Tax Considerations" and "Risk Factors Relating to the Securities" in the accompanying product supplement and "Summary Risk Factors" in this pricing supplement.

Due to the lack of any controlling legal authority, there is substantial uncertainty regarding the U.S. federal tax consequences of an investment in the securities. In connection with any information reporting requirements we may have in respect of the securities under applicable law, we intend (in the absence of an administrative determination or judicial ruling to the contrary) to treat the securities for U.S. federal income tax purposes as prepaid forward contracts with associated coupon payments that will be treated as gross income to you at the time received or accrued in accordance with your regular method of tax accounting. We expect that our counsel will advise us that, based on current market conditions, this treatment of the securities is reasonable under current law, but that it is unable to conclude affirmatively that this treatment is more likely than not to be upheld, and that alternative treatments are possible. The information set forth under this section remains subject to confirmation by our counsel following the pricing of the securities. If that information cannot be confirmed by our counsel, you may be asked to accept revisions to that information in connection with your purchase. Under these circumstances, if you decline to accept revisions to that information, your purchase of the securities will be canceled.

Assuming this treatment of the securities is respected and subject to the discussion in "United States Federal Tax Considerations" in the accompanying product supplement, the following U.S. federal income tax consequences should result under current law:

We do not plan to request a ruling from the IRS regarding the treatment of the securities. An alternative characterization of the securities could materially and adversely affect the tax consequences of ownership and disposition of the securities, including the timing and character of income recognized. In addition, the U.S. Treasury Department and the IRS have requested comments on various issues regarding the U.S. federal income tax treatment of "prepaid forward contracts" and similar financial instruments and have indicated that such transactions may be the subject of future regulations or other guidance. Furthermore, members of Congress have proposed legislative changes to the tax treatment of derivative contracts. Any legislation, 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, possibly with retroactive effect. You should consult your tax adviser regarding possible alternative tax treatments of the securities and potential changes in applicable law.

Withholding Tax on Non-U.S. Holders. Because significant aspects of the tax treatment of the securities are uncertain, persons having withholding responsibility in respect of the securities may withhold on any coupon payment paid to Non-U.S. Holders (as defined in the accompanying product supplement), generally at a rate of 30%. To the extent that we have (or an affiliate of ours has) withholding responsibility in respect of the securities, we intend to so withhold. In order to claim an exemption from, or a reduction in, the 30% withholding, you may need to comply with certification requirements to establish that you are not a U.S. person and are eligible for such an exemption or reduction under an applicable tax treaty. You should consult your tax adviser regarding the tax treatment of the securities, including the possibility of obtaining a refund of any amounts withheld and the certification requirement described above.

As discussed under "United States Federal Tax Considerations-Tax Consequences to Non-U.S. Holders" in the accompanying product supplement, Section 871(m) of the Code and Treasury regulations promulgated thereunder ("Section 871(m)") generally impose a 30% withholding tax on dividend equivalents paid or deemed paid to Non-U.S. Holders with respect to certain financial instruments linked to U.S. equities ("U.S. Underlying Equities") or indices that include U.S. Underlying Equities. Section 871(m) generally applies to instruments that substantially replicate the economic performance of one or more U.S. Underlying Equities, as determined based on tests set forth in the applicable Treasury regulations. However, the regulations, as modified by an IRS notice, exempt financial instruments issued prior to January 1, 2027 that do not have a "delta" of one. Based on the terms of the securities and market conditions as of the date of this preliminary pricing supplement, we expect that the securities will not be treated as transactions that have a "delta" of one within the meaning of the regulations with respect to any U.S. Underlying Equity and, therefore, should not be subject to withholding tax under Section 871(m). However, the final determination regarding the treatment of the securities under Section 871(m) will be made as of the pricing date for the securities, and it is possible that the securities will be subject to withholding tax under Section 871(m) based on the circumstances as of that date.

A determination that the securities are not subject to Section 871(m) is not binding on the IRS, and the IRS may disagree with this treatment. Moreover, Section 871(m) is complex and its application may depend on your particular circumstances, including your other transactions. You should consult your tax adviser regarding the potential application of Section 871(m) to the securities.

We will not be required to pay any additional amounts with respect to amounts withheld.

You should read the section entitled "United States Federal Tax Considerations" in the accompanying product supplement.

You should also consult your tax adviser regarding all aspects of the U.S. federal income and estate tax consequences of an investment in the securities and any tax consequences arising under the laws of any state, local or non-U.S. taxing jurisdiction.

Supplemental Plan of Distribution

CGMI, an affiliate of Citigroup Global Markets Holdings Inc. and the underwriter of the sale of the securities, is acting as principal and will not receive any underwriting fee for any securities sold in this offering. However, CGMI and its affiliates may profit from expected hedging activity

related to this offering. From these expected hedging profits, CGMI will pay selected dealers participating in the distribution of the securities a structuring fee of up to $3.75 for each security sold in this offering. We may also engage other firms to provide marketing or promotional services in connection with the distribution of the securities. CGMI will pay these service providers a fee of up to $3.50 per security in consideration for providing marketing, education, structuring or referral services with respect to financial advisors or selected dealers. For the avoidance of doubt, any fees or selling concessions described in this pricing supplement will not be rebated if we redeem the securities prior to maturity.

See "Plan of Distribution; Conflicts of Interest" in the accompanying product supplement and "Plan of Distribution" in each of the accompanying prospectus supplement and prospectus for additional information.

Valuation of the Securities

CGMI calculated the estimated value of the securities set forth on the cover page of this pricing supplement based on proprietary pricing models. CGMI's proprietary pricing models generated an estimated value for the securities by estimating the value of a hypothetical package of financial instruments that would replicate the payout on the securities, which consists of a fixed-income bond (the "bond component") and one or more derivative instruments underlying the economic terms of the securities (the "derivative component"). CGMI calculated the estimated value of the bond component using a discount rate based on our internal funding rate. CGMI calculated the estimated value of the derivative component based on a proprietary derivative-pricing model, which generated a theoretical price for the instruments that constitute the derivative component based on various inputs, including the factors described under "Summary Risk Factors-The value of the securities prior to maturity will fluctuate based on many unpredictable factors" in this pricing supplement, but not including our or Citigroup Inc.'s creditworthiness. These inputs may be market-observable or may be based on assumptions made by CGMI in its discretionary judgment.

The estimated value of the securities is a function of the terms of the securities and the inputs to CGMI's proprietary pricing models. As of the date of this preliminary pricing supplement, it is uncertain what the estimated value of the securities will be on the pricing date because certain terms of the securities have not yet been fixed and because it is uncertain what the values of the inputs to CGMI's proprietary pricing models will be on the pricing date.

For a period of approximately three months following issuance of the securities, the price, if any, at which CGMI would be willing to buy the securities from investors, and the value that will be indicated for the securities on any brokerage account statements prepared by CGMI or its affiliates (which value CGMI may also publish through one or more financial information vendors), will reflect a temporary upward adjustment from the price or value that would otherwise be determined. This temporary upward adjustment represents a portion of the hedging profit expected to be realized by CGMI or its affiliates over the term of the securities. The amount of this temporary upward adjustment will decline to zero on a straight-line basis over the three-month temporary adjustment period. However, CGMI is not obligated to buy the securities from investors at any time. See "Summary Risk Factors-The securities will not be listed on any securities exchange and you may not be able to sell them prior to maturity."

Contact

Clients may contact their local brokerage representative. Third-party distributors may contact Citi Structured Investment Sales at (212) 723-7005.

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