Wilmerding is a borough in Allegheny County, Pennsylvania, United States. The population was 1,781 at the 2020 census. It is located 12 miles (19 km) southeast of Pittsburgh. At the start of the twentieth century, it had extensive foundries and machine shops of the Westinghouse Air Brake Company. Wilmerding is adjacent to the borough of Turtle Creek, which takes its name from a small stream that flows past both places.

The Westinghouse Air Brake Technologies Corporation was founded on September 28, 1869 by George Westinghouse in Pittsburgh, Pennsylvania. Earlier in the year he had invented the railway air brake in New York state.