The Safety Appliance Act is a United States federal law that made air brakes and automatic couplers mandatory on all trains in the United States. It was enacted on March 2, 1893, and took effect in 1900, after a seven-year grace period. The act is credited with a sharp drop in accidents on American railroads in the early 20th century.

A coupling or coupler is a mechanism, typically located at each end of a rail vehicle, that connects them together to form a train. The equipment that connects the couplers to the vehicles is the draft gear or draw gear, which must absorb the stresses of the coupling and the acceleration of the train.