Winchester Bay, formerly Umpqua City, is an unincorporated community in Douglas County, Oregon, United States. For statistical purposes, the United States Census Bureau has defined Winchester Bay as a census-designated place. The census definition of the area may not precisely correspond to local understanding of the area with the same name. The population of the CDP was 382 at the 2010 census. The community of Umpqua City was established in 1850.