Riverside is a neighborhood/section in the town of Greenwich in Fairfield County, Connecticut, United States. As of the 2020 census, it had a population of 8,843. The town of Greenwich is one political and taxing body, but consists of several distinct sections or neighborhoods, such as Banksville, Byram, Cos Cob, Glenville, Mianus, Old Greenwich, Riverside, and Greenwich. Of these neighborhoods, three have separate postal names and ZIP codes.