Teamsters Union, in full, International Brotherhood of Teamsters, Chauffeurs, Warehousemen, and Helpers of America, one of the largest trade unions in the world, founded in 1903. In 2005 the membership consisted of about 1.4 million people working in such diversified fields as transportation, warehousing, health care, office management, and construction, as well as many workers in the bakery, dairy, brewery, and food-processing industries. The Teamsters also represent a growing number of public employees, especially in corrections.

Because of its size, the Teamsters Union wields great economic power, and its pension fund is a significant investment resource. Since the 1950s, the union has repeatedly been investigated for corrupt practices, and several of its presidents have been imprisoned on criminal charges. The union was expelled from the American Federation of Labor and Congress of Industrial Organizations (AFL-CIO) in 1957, but was allowed to rejoin in 1987. However, the Teamsters withdrew from the AFL-CIO in 2005, arguing that the labor federation was not doing enough to organize nonunion workers. The Teamsters joined the newly formed Change to Win Coalition, along with the Service Employees International Union (SEIU) and several other unions.

The union is organized into five regions that assist some 570 locals in the United States, Canada, and Puerto Rico with regional contracts and negotiations. Headquarters is in Washington, D.C.

See also Labor Unions in the United States.