in U.S. history, a political-action movement that from 1866 to 1873 sought to improve working conditions through legislative reform rather than through collective bargaining.

The NLU began in 1866 with a convention in Baltimore, Md., called to organize skilled and unskilled labourers, farmers, and reformers into a coalition that would pressure Congress to pass a law limiting the workday to eight hours. Seventy-seven delegates attended the convention, and during its brief existence the National Labor Union may have had as many as 500,000 members.

Acting on the belief that owners and workers shared identical interests, the NLU was opposed to strikes. It relied increasingly on political action to meet its goals and in 1872 transformed itself into the National Labor Reform Party. As such it nominated David Davis (Davis, David) of Illinois, associate justice of the U.S. Supreme Court, as its presidential candidate. Davis withdrew his candidacy, however, and the party made a poor showing at the polls. After holding one last convention in 1873, the National Labor Union collapsed and disappeared.