Oswego County Courthouse is a historic courthouse located at Oswego in Oswego County, New York. It was built in 1859-1860 and altered in 1891 and again in 1962. The two story building rises above a cruciform plan and is constructed of load bearing masonry walls faced with smooth ashlar limestone. It features a portico surmounted by a domed cupola. It was designed by architect Horatio Nelson White (1814–1892). It was listed on the National Register of Historic Places in 2000.