The Homestead strike, also known as the Homestead steel strike, Homestead massacre, or Battle of Homestead, was an industrial lockout and strike that occurred in the United States, in 1892. It began on July 1, 1892, culminating in a battle in which strikers defeated private security agents on July 6, 1892. The governor responded by sending in the National Guard to protect strikebreakers. The dispute occurred at the Homestead Steel Works in the Pittsburgh-area town of Homestead, Pennsylvania, between the Amalgamated Association of Iron and Steel Workers (the AA) and the Carnegie Steel Company. The final result was a major defeat for the union strikers and a setback for their efforts to unionize steelworkers. The battle was a pivotal event in U.S. labor history.

Carnegie Steel made major technological innovations in the 1880s, especially the installation of the open-hearth system at Homestead in 1886. It now became possible to make steel suitable for structural beams and for armor plate for the United States Navy, which paid far higher prices for the premium product. In addition, the plant moved increasingly toward the continuous system of production. Carnegie installed vastly improved systems of material-handling, like overhead cranes, hoists, charging machines, and buggies. All of this greatly sped up the process of steelmaking, and allowed the production of vastly larger quantities of the product. As the mills expanded, the labor force grew rapidly, especially with unskilled workers. However, while Carnegie Steel grew and progressed, workers at Homestead were seeing their wages drop.

The Amalgamated Association of Iron and Steel Workers (AA) was an American labor union formed in 1876. It was a craft union representing skilled iron and steelworkers.

The AA's membership was concentrated in ironworks west of the Allegheny Mountains. The union negotiated national uniform wage scales on an annual basis; helped regulate working hours, workload levels and work speeds; and helped improve working conditions. It also acted as a hiring hall, helping employers find scarce puddlers and rollers.

The AA organized the independently owned Pittsburgh Bessemer Steel Works in Homestead in 1881. The AA engaged in a strike at the Homestead works on January 1, 1882, in an effort to prevent management from including a non-union clause in the workers' contracts, known as a "yellow-dog contract". The violence occurred on both sides, and the plant brought in numerous strikebreakers. The strike ended on March 20, in a complete victory for the union.

The AA struck the steel plant again on July 1, 1889, when negotiations for a new three-year collective bargaining agreement failed. The strikers seized the town and once again made common cause with various immigrant groups. Backed by 2,000 townspeople, the strikers drove off a trainload of strikebreakers on July 10. When the sheriff returned with 125 newly deputized agents two days later, the strikers rallied 5,000 townspeople to their cause. Although victorious, the union agreed to significant wage cuts that left tonnage rates less than half those at the nearby Jones and Laughlin works, where technological improvements had not yet been made.

Carnegie officials conceded that the AA essentially ran the Homestead plant after the 1889 strike. The union contract contained 58 pages of footnotes defining work rules at the plant and strictly limited management's ability to maximize output.

For its part, the AA saw substantial gains after the 1889 strike. Membership doubled, and the local union treasury had a balance of $146,000. The Homestead union grew belligerent, and relationships between workers and managers became tense.