Colby is a city in Clark and Marathon counties in the U.S. state of Wisconsin. It is part of the Wausau, Wisconsin Metropolitan Statistical Area. The population was 1,616 at the 2000 census. The city is located partially within the Town of Colby, though it is politically independent.
The city of Colby took its name from the railway station on the Wisconsin Central Railway, which had been built through that country a short time before, and the station was named for Gardner L. Colby, father of Charles L. Colby, who was so long identified with the railway. Colby is the birthplace of Colby cheese. There is a historical marker downtown commemorating the development of Colby cheese by Joseph Steinwand in the 1880s.
Colby is located at 44°54′36″N 90°19′1″W / 44.91°N 90.31694°W / 44.91; -90.31694 (44.910186, -90.317058).