The Mount Sterling Commercial Historic District is a historic business district located in downtown Mount Sterling, Illinois. The district, located immediately south of the Brown County Courthouse, includes four entire city blocks and parts of four others; 38 buildings, of which 35 are contributing buildings, are in the district.

Nearly all of the buildings in the district are Italianate commercial buildings; the only exceptions are a Classical Revival bank building and the courthouse, which incorporates both Italianate and Classical Revival elements. Two government buildings are located in the district: the 1868 courthouse and the Mount Sterling public library, which is located in a former hardware store.

The district was added to the National Register of Historic Places on May 8, 1987.