Cos Cob is a neighborhood and census-designated place in the town of Greenwich, Connecticut. It is located at 41.033 north, 73.6 west, on the Connecticut shoreline in southern Fairfield County. It had a population of 6,770 at the 2010 census. Cos Cob is located on the western side of the mouth of the Mianus River. The American Impressionist Cos Cob Art Colony flourished in the late 19th and early 20th centuries.