US Post Office—Lancaster is a historic post office building located at Lancaster in Erie County, New York.

It was designed and built 1938–1939, and is one of a number of post offices in New York State designed by the Office of the Supervising Architect of the Treasury Department, Louis A. Simon.

The interior features a mural by Arthur Getz painted in 1940 and titled "Early Commerce in the Erie Canal Region.

"[3] It was listed on the National Register of Historic Places in 1989.

This article about a historic property or district in Erie County, New York, that is listed on the National Register of Historic Places, is a stub.