The American Federation of Labor (AFL) was a national federation of labor unions in the United States founded in Columbus, Ohio, in December 1886 by an alliance of craft unions disaffected from the Knights of Labor, a national labor union. Samuel Gompers was elected the full-time president at its founding convention and reelected every year, except one, until his death in 1924. He became the major spokesperson for the union movement.

The AFL was the largest union grouping in the United States for the first half of the 20th century, even after the creation of the Congress of Industrial Organizations (CIO) by unions that were expelled by the AFL in 1935. The Federation was founded and dominated by craft unions throughout its first fifty years, after which many craft union affiliates turned to organizing on an industrial union basis to meet the challenge from the CIO in the 1940s. In 1955, the AFL merged with the CIO to create the AFL-CIO, which has comprised the longest lasting and most influential labor federation in the United States to this day.