Old Greenwich is a neighborhood/section and census-designated place in Greenwich in Fairfield County, Connecticut, United States. As of the 2010 census it had a population of 6,611. It was founded in 1641. Old Greenwich has become extremely popular for home buyers and currently ranks at 7th place among the nation's wealthiest communities in an annual Bloomberg report published March 5, 2018, "America's 100 Richest Places".
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 (sometimes referred to as central, or downtown, Greenwich). Of these neighborhoods, three (Cos Cob, Old Greenwich, and Riverside) have separate postal names and ZIP codes.