Jefferies Financial Group Inc. 美国招股说明书（2026年6月17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 June 16, 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 Contingent Coupon Barrier Notes due June 18, 2031 Linked to the Worst-Performing of the iShares®MSCI Emerging Markets ETF, the Nasdaq-100 Index® The Senior Autocallable Contingent Coupon Barrier Notes due June 18, 2031 Linked to the Worst-Performing of the iShares®MSCI Emerging Markets ETF, the Nasdaq-100 Index®and theRussell 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 and prospectus, 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. Issuer: Title of the Notes: Senior Autocallable Contingent Coupon Barrier Notes due June 18, 2031 Linked to the Worst-Performing of the iShares®MSCI Emerging Markets ETF,the Nasdaq-100 Index®and the Russell 2000®Index Aggregate Principal Amount:Issue Price:Stated Principal Amount:Pricing Date: . We may increase the Aggregate Principal Amount prior to the Original Issue Date but are not required to do so.$1,000 per Note$1,000 per Note $ June 16, 2026June 18, 2026 (2 Business Days after the Pricing Date) Monthly, beginning on July 16, 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 theaccompanying product supplement. Coupon Payment Dates: Monthly, beginning on December 16, 2026, as set forth on page PS-2. The Call Observation Dates are subject to postponement as described in theaccompanying 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 Call Observation Dates: Call Payment Dates: accompanying product supplement. Valuation Date:Maturity Date:Underlying: June 16, 2031, subject to postponement as described in the accompanying product supplement. June 18, 2031, which may be postponed if the Valuation Date is postponed as described in the accompanying product supplement.The worst-performing of the iShares®MSCI Emerging Markets ETF (the “EEM”), the Nasdaq-100 Index®(the “NDX”) and the Russell 2000®Index (the“RTY”). Please see “The Underlyings” below. Worst-Performing Underlying:Coupon Feature: Contingent Coupon Payments. The Notes will pay a Contingent Coupon Payment of $10.21 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. 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 holda Payment at Maturity that is equal to the Stated Principal Amount If 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 atMaturity 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 on the finalCoupon Observation Date is greater than or equal to its Coupon Barrier. Initial Value: With respect to each of theNDX and the RTY, the Index Closing Value of the Underlying on the Pricing Date.With respect to theEEM, the