Winthrop is a town in Kennebec County, Maine, United States. The population was 6,092 at the 2010 census. Winthrop's population, however, approximately doubles during the summer months as part-year residents return to seasonal camps located on the shores of Winthrop's Lakes and Ponds. A recreational area located among lakes, the town includes the villages of Winthrop and East Winthrop.