The Knights of Labor (K of L) (officially "Noble and Holy Order of the Knights of Labor") is the largest and one of the most important American labor organizations of the 1880s.

Its most important leader is Terence V. Powderly.

The Knights promote the social and cultural uplift of the workingman, reject Socialism and radicalism, demand the eight-hour day, and promote the producers ethic of republicanism.

In some cases, it acts as a labor union, negotiating with employers, but it is never well organized, and after a rapid expansion in the mid-1880s, it suddenly loses its new members and becomes a small operation again.It is established in 1869, reaches 28,000 members in 1880, then jumpssto 100,000 in 1885.

Then it mushrooms to nearly 800,000 members in 1886, but its frail organizational structure cannot cope and it is battered by charges of failure and violence.

Most members abandon the movement in 1886-87, leaving at most 100,000 in 1890.

Remnants of the Knights of Labor continue in existence until 1949, when the group's last 50-member local drops its affiliation.