William B. Green was an American trade union leader. Green is best remembered as the president of the American Federation of Labor from 1924 to 1952. He was a strong supporter for labor-management co-operation and was on the frontline for wage and benefit protections and industrial unionism legislation. As president of the AFL, he continued the development of the federation away from the foundations of "pure and simple unionism" to a more politically active "social reform unionism."