X0609 4 2026-06-02 0 0001333274 MERCER INTERNATIONAL INC. MERC 0001260893 MCCARTNEY WILLIAM true SUITE 1120-700 WEST PENDER STREET VANCOUVER BRITISH COLUMBIA A1 V6C 1G8 BRITISH COLUMBIA, CANADA 1 0 0 0 0 Deferred Stock Units 2026-06-02 4 A 0 41250 A Common Stock 41250 106156 D Represents deferred stock units ("DSUs") issued by Mercer International Inc. ("Mercer") as a grant to the Reporting Person under Mercer's non-employee director compensation program and the Amended and Restated 2022 Stock Incentive Plan in connection with his role as a director and Chairperson of Mercer's board of directors and in respect of the board term commencing June 1, 2026 and ending at its next regularly scheduled annual general meeting in 2027 (the "2027 AGM"). Each DSU vests on the earlier of the one year anniversary of the grant date or the date of the 2027 AGM and represents the right to receive one share of Mercer's common stock and dividend equivalents after the Reporting Person ceases to be a director of Mercer, unless deferred in accordance with its terms. /s/William McCartney 2026-06-02