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 isnot permitted. PRELIMINARY PRICING SUPPLEMENT(to Product Supplement no. 5, dated May 11, 2026,Prospectus Supplement dated May 11, 2026and Prospectus dated May 11, 2026) SUBJECT TO COMPLETION, DATED June 1, 2026 $Jefferies Jefferies Financial Group Inc.Senior Autocallable Contingent Coupon Barrier Notes due June 10, 2031Linked to the Worst-Performing of the Nasdaq-100 Index®, the Russell 2000®Index and the State Street®Consumer Staples Select SectorSPDR®ETF The Senior Autocallable Contingent Coupon Barrier Notes due June 10, 2031 Linked to the Worst-Performing of the Nasdaq-100 Index®, the Russell 2000®Index and the State Street®Consumer Staples Select Sector SPDR®ETF (the “Notes”) are senior unsecured obligations of Jefferies Financial Group Inc. The Notes have the terms described in the accompanyingproduct supplement, prospectus supplement and prospectus, as supplemented or modified by this pricing supplement. The Notes are issued as part of our Series A Global Medium-TermNotes program. All payments are subject to our credit risk. If we default on our obligations, you could lose some or a significant portion of your investment. These Notes are not securedobligations and you will not have any security interest in, or otherwise have any access to, any Underlying or the securities represented by any Underlying.SUMMARY OF TERMS Senior Autocallable Contingent Coupon Barrier Notes due June 10, 2031 Linked to the Worst-Performing of the Nasdaq-100 Index®, the Russell 2000®Index and the State Street®Consumer Staples Select Sector SPDR®ETFAggregate Principal Amount:$. We may increase the Aggregate Principal Amount prior to the Original Issue Date but are not required to do so. Title of the Notes: Issue Price:Stated Principal Amount:Pricing Date:Original Issue Date:Coupon Observation Dates: June 10, 2026 (3 Business Days after the Pricing Date)Monthly, beginning on July 6, 2026, as set forth on page PS-2. The Coupon Observation Dates are subject to postponement as described in the accompanying product supplement. As set forth on page PS-2. The Coupon Payment Dates may be postponed if the related Coupon Observation Date is postponed as described in the accompanying product supplement.Monthly, beginning on December 7, 2026, as set forth on page PS-2. The Call Observation Dates are subject to postponement as described in the Coupon Payment Dates: Call Observation Dates: accompanying product supplement.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 accompanying Call Payment Dates: product supplement. June 5, 2031, subject to postponement as described in the accompanying product supplement. Valuation Date:Maturity Date:Underlying: The worst-performing of the Nasdaq-100 Index®(the “NDX”), the Russell 2000®Index (the “RTY”) and the State Street®Consumer Staples Select SectorSPDR®ETF (the “XLP”). Please see “The Underlyings” below.Worst-Performing Underlying:The Underlying with the lowest Observation Value or Final Value, as applicable, as compared to its Initial Value. Coupon Feature: Contingent Coupon Payments. The Notes will pay a Contingent Coupon Payment of $11.46 on the applicable Coupon Payment Date if the ObservationValue of the Worst-Performing Underlying on the applicable monthly Coupon Observation Date is greater than or equal to its Coupon Barrier. Autocallable Notes. The Notes will be automatically called if the Observation Value of the Worst-Performing Underlying on any Call Observation Date Call Feature: (beginning approximately six months after the Pricing Date) is equal to or greater than its Call Value. If your Notes are called, you will receive the CallPayment on the applicable Call Payment Date, and no further amounts will be payable on the Notes.The Stated Principal Amount plus any Contingent Coupon Payment that may otherwise be due on the applicable Call Payment Date. Call Payment:Payment at Maturity: If the Final Value of the Worst-Performing Underlying is greater than or equal to its Threshold Value, you will receive for each Note that you hold a Payment at Maturity that is equal to the Stated Principal AmountIf the Final Value of the Worst-Performing Underlying is less than its Threshold Value, you will receive for each Note that you hold a Payment at Maturity that is less than the Stated Principal Amount of each Note that will equal: 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.The Payment at Maturity will also include the final Contingent Coupon Payment if the Observation Value of the Worst-Performing Underlying o