American labour leader, elected president of the American Federation of Labor–Congress of Industrial Organizations (AFL-CIO) in 1995. Sweeney won an uncontested reelection during the AFL-CIO convention in July 2005, but, in the same week, the federation lost three of its biggest unions when the Teamsters (Teamsters Union), the SEIU, and the United Food and Commercial Workers announced their withdrawal from the AFL-CIO.

Sweeney is the son of Irish immigrants. His mother was a domestic worker, and his father, a bus driver, was a member of the Transport Workers Union. Sweeney studied economics at Iona College and began his career as a research assistant with the International Ladies' Garment Workers' Union. In 1961 he joined the Service Employees International Union (SEIU) as a contract director for New York City Local 32B, and he became president of the local in 1976. Elected president of the SEIU in 1980, he was credited with boosting membership by 75 percent (to more than 1 million) during his 15-year tenure. His recruitment success represented a sharp contrast to the declining enrollments in many American unions, and they helped Sweeney win the AFL-CIO presidency. Sweeney's strategy was to increase labour's visibility and political clout, and to that end the AFL-CIO contributed $35 million toward many 1996 political campaigns, including the reelection campaign of President Bill Clinton.

Critics claimed, however, that Sweeney spent too much time lobbying politicians while doing little to slow the overall membership declines. A major rebuke occurred in March 2001 when the 500,000-member United Brotherhood of Carpenters and Joiners (UBC), led by its president, Douglas J. McCarron, pulled out of the AFL-CIO.