The Belvidere U.S. Post Office is a historic building located in the Illinois city's downtown business district.

It was added to the National Register of Historic Places as United States Post Office-Belvidere in 2000.

[2] The Belvidere U.S. Post Office was built in the Classical Revival style of architecture and was designed by Supervising Architect of the U.S. Treasury James Knox Taylor.

The interior dome, the broken pediment over the entryway (a Greek Revival form), finely dressed stonework, a monumental scale, and sculptural stone details are all commonly found among Classical Revival-styled buildings.

[2] The U.S. Post Office in Belvidere, Illinois was added to the National Register of Historic Places on May 11, 2000.