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.

George Westinghouse purchased land in the Turtle Creek valley in 1887 and 1888 as a site for his Westinghouse Air Brake Company and related facilities. Westinghouse then sold the land to the East Pittsburgh Improvement Company, incorporated in December 1888, to develop the site, and it began the sale of lots in June 1889.

Wilmerding's most notable historic structure is the Westinghouse Air Brake Company General Office Building (1889–1890, rebuilt 1896), designed by Frederick J. Osterling and now listed on the National Register of Historic Places.

The community was named for Joanna Wilmerding (Bruce) Negley, wife of William B. Negley, who in turn was a local landowner and nephew of Thomas Mellon.

Wilmerding officially became a borough on March 8, 1890. The first burgess (mayor) was T. W. Walsh, elected on June 14, 1890.

Wilmerding neighbors five borders, including Monroeville to the northeast, Wall to the east, East McKeesport to the south, North Versailles Township to the southwest, and Turtle Creek (via Greensburg Pike/Lincoln Highway Bridge) to the northwest.