X0202 SCHEDULE 13D/A 0001193805-10-000792 0000897485 XXXXXXXX LIVE 11 Common Stock, par value $1.00 05/19/2026 false 0001333274 588056101 MERCER INTERNATIONAL INC.

Suite 1120, 700 West Pender Street Vancouver A1 V6C 1G8

Peter R. Kellogg (212) 389-5841 48 Wall Street, 30th Floor New York NY 10005 0000897485 N Peter R. Kellogg OO N X1 25380929.00 0.00 25380929.00 0.00 24469540.00 N 37.9 IN Common Stock, par value $1.00 MERCER INTERNATIONAL INC. Suite 1120, 700 West Pender Street Vancouver A1 V6C 1G8 As of the close of business on May 19, 2026, Mr. Kellogg beneficially owned an aggregate of 25,380,929 shares, constituting approximately 37.9% of the shares outstanding. As of the close of business on May 19, 2026, Mr. Kellogg beneficially owned an aggregate of 25,380,929 shares, constituting approximately 37.9% of the shares outstanding. During May 12, 2026 through May 19, 2026, entities controlled by Mr. Kellogg purchased an aggregate of 1,000,000 shares at prices ranging from approximately $0.84 to $0.96 per share through the Nasdaq Stock Market. All such transactions have been reported on a Form 4 filed by Mr. Kellogg. Peter R. Kellogg /s/ Marguerite Gorman 05/19/2026