Jefferies Financial Group Inc. 美股招股说明书（2026年6月1日版）

The information in this preliminary pricing supplement is not complete and may be changed without notice. This preliminary pricingsupplement is not an offer to sell these securities, nor a solicitation of an offer to buy these securities, in any jurisdiction where the offering is SUBJECT TO COMPLETION, DATED May 29, 2026 PRELIMINARY PRICING SUPPLEMENT(to Product Supplement no. 5, dated May 11, 2026, Prospectus Supplement dated May 11, 2026and Prospectus dated May 11, 2026) Jefferies Jefferies Financial Group Inc. Senior Autocallable Barrier Notes due June 30, 2031Linked to the Worst-Performing of the Dow Jones Industrial Average®, the Nasdaq-100 Index® The Senior Autocallable Barrier Notes due June 30, 2031 Linked to the Worst-Performing of the Dow Jones Industrial Average®, the Nasdaq-100 Index®and the Russell 2000®Index (the“Notes”) are senior unsecured obligations of Jefferies Financial Group Inc. The Notes have the terms described in the accompanying product supplement, prospectus supplement andprospectus, as supplemented or modified by this pricing supplement. The Notes are issued as part of our Series A Global Medium-Term Notes program.All payments are subject to our credit risk. If we default on our obligations, you could lose some or a significant portion of your investment. These Notes are not securedobligations and you will not have any security interest in, or otherwise have any access to, any Underlying or the securities represented by any Underlying. SUMMARY OF TERMSIssuer:Title of the Notes: Jefferies Financial Group Inc.Senior Autocallable Barrier Notes due June 30, 2031 Linked to the Worst-Performing of the Dow Jones Industrial Average®, the Nasdaq-100 Index®and the Russell 2000®IndexAggregate Principal Amount:$. We may increase the Aggregate Principal Amount prior to the Original Issue Date but are not required to do so.$1,000 per Note Issue Price:Stated Principal Amount:Pricing Date:Original Issue Date:Call Observation Dates: Call Payment Dates: As set forth on page PS-2. The Call Payment Dates may be postponed if the related Call Observation Date is postponed as described in the accompanyingproduct supplement.June 26, 2031 (which is also the final Call Observation Date), subject to postponement as described in the accompanying product supplement. Valuation Date:Maturity Date:Underlying: June 30, 2031, which may be postponed if the Valuation Date is postponed as described in the accompanying product supplement.The worst-performing of the Dow Jones Industrial Average®(the “INDU”), the Nasdaq-100 Index®(the “NDX”) and the Russell 2000®Index (the “RTY”).Please see “The Underlyings” below. Worst-PerformingUnderlying:Call Feature: The Underlying with the lowest Observation Value or Final Value, as applicable, as compared to its Initial Value. Autocallable Notes. The Notes will be automatically called if the Observation Value of the Worst-Performing Underlying on any Call Observation Date(beginning approximately one year after the Pricing Date) is equal to or greater than its Call Value. If your Notes are called, you will receive the applicableCall Payment on the applicable Call Payment Date, and no further amounts will be payable on the Notes.The Stated Principal Amount plus the applicable Call Premium. Call Payment:Call Premium: are “Snowball Coupon Notes” for purposes of the accompanying product supplement and, for purposes of this pricing supplement, references in theaccompanying product supplement to “Snowball Coupon Payment” shall be deemed to refer to “Call Premium”.If the Notes are not called prior to maturity and the Final Value of the Worst-Performing Underlying is greater than or equal to its Threshold Value, Payment at Maturity: In this scenario the Payment at Maturity will be less than the Stated Principal Amount and you could lose some or all of your investment.With respect to each Underlying, the Index Closing Value of the Underlying on the Pricing Date.With respect to each Underlying, the Index Closing Value of the Underlying on the applicable Call Observation Date.With respect to each Underlying, the Index Closing Value of the Underlying on the Valuation Date. Initial Value:Observation Value:Final Value:Call Value:Threshold Value:Specified Currency:CUSIP/ISIN:Book-entry or CertificatedNote:Business Day:Agent:Calculation Agent:Trustee:Estimated value on thePricingDate:Use of Proceeds:Listing: New YorkJefferies LLC, a wholly-owned subsidiary of Jefferies Financial Group Inc. See “Supplemental Plan of Distribution.”Jefferies Financial Services, Inc., a wholly owned subsidiary of Jefferies Financial Group Inc.The Bank of New York MellonApproximately $933.70 per Note, or within $30.00 of that estimate. Please see “The Notes” below. Conflict of Interest:Jefferies LLC, the broker-dealer subsidiary of Jefferies Financial Group Inc., is a member of FINRA and will participate in the distribution of the notes beingoffered hereby. Accordingly, the offering is subjec