The Knights of Labor, officially the Noble and Holy Order of the Knights of Labor, was an American labor federation that was active in the late 19th century, especially the 1880s. It operated in the United States as well in Canada, and had chapters also in Great Britain and Australia. Its most important leader was Terence V. Powderly. The Knights of Labor promoted the social and cultural uplift of the worker, and demanded the eight-hour day. In some cases it acted as a labor union, negotiating with employers, but it was never well organized or funded. It was notable in its ambition to organize across lines of gender and race and in the inclusion of both skilled and unskilled labor. After a rapid expansion in the mid-1880s, it suddenly lost its new members and became a small operation again. The Knights of Labor had served, however, as the first mass organization of the white working class of the United States.

Terence Vincent Powderly was an American labor union leader, politician and attorney, best known as head of the Knights of Labor in the late 1880s. Born in Carbondale, Pennsylvania, he was later elected mayor of Scranton, Pennsylvania, for three 2-year terms, starting in 1878. A Republican, he served as the United States Commissioner General of Immigration in 1897. The Knights of Labor was one of the largest American labor organizations of the 19th century, but Powderly was a poor administrator and could barely keep it under control. His small central office could not supervise or coordinate the many strikes and other activities sponsored by union locals. Powderly believed that the Knights were an educational tool to uplift the workingman, and he often cautioned against the use of strikes to achieve workers' goals.