John Llewellyn Lewis (February 12, 1880 – June 11, 1969) was an American leader of organized labor who served as president of the United Mine Workers of America from 1920 to 1960. He was a major player in the history of coal mining. He was the driving force behind the founding of the Congress of Industrial Organizations, which established the United Steel Workers of America and helped organize millions of other industrial workers in the 1930s. After resigning as head of the CIO in 1941, he took the Mine Workers out of the CIO in 1942, then back into the American Federation of Labor (AFL) in 1944.

A leading liberal, he played a major role in helping Franklin D. Roosevelt win a landslide in 1936, but as an isolationist broke with Roosevelt in 1940 on foreign policy. Lewis was a brutally effective and aggressive fighter and strike leader who gained high wages for his membership while steamrolling over his opponents, including the United States government. Lewis was one of the most controversial and innovative leaders in the history of labor, gaining credit for building the industrial unions of the CIO into a political and economic powerhouse to rival the AFL, yet was widely hated as he called nationwide coal strikes damaging the American economy in the middle of World War II. His massive leonine head, forestlike eyebrows, firmly set jaw, powerful voice and ever-present scowl thrilled his supporters, angered his enemies, and delighted cartoonists. Coal miners for 40 years hailed him as the benevolent dictator who brought high wages, pensions and medical benefits, and damn the critics.