Jonas Donald Gaines (January 9, 1914 – August 6, 1998), nicknamed "Lefty", was an American baseball pitcher in the Negro leagues. He played professionally from 1937 to 1953 with several teams. A native of New Roads, Louisiana, Gaines served in the US Army during World War II. He pitched in three East-West All-Star Games; 1942, 1946, and 1950. Gaines also pitched in the Cuban League and the Pacific League. He died in Baker, Louisiana in 1998 at age 84.