Cos Cob has a population of a little over 6,300 and is a neighborhood in the town of Greenwich, Connecticut in Fairfield county.

The community is situated on Cos Cob Harbor, a sheltered area on the north side of Long Island Sound. Cos Cob flourished as a seaport during the 1700's and 1800's. At the turn of the 19th century, Cos Cob evolved into an intellectual and artist colony playing host to the likes of Eugene O'Neill, Willa Cather and Anya Seton (whose father, Ernest Thompson Seton, started the Boy Scouts of America in Cos Cob). The town is named after a man called Coe, and at its founding was called Coe's Cob. Cos Cob's role as a commercial shipping port, supplying potatoes and apples to New York City, disappeared with the appearance of the railroad and damming of the Mianus River. The river is now one source of the town's drinking water. Cos Cob today is a robust community with a central downtown shopping district along Route One.

The American Impressionist Cos Cob Art Colony flourished in the late 1800s and early 1900s. An offshoot of the group, the Art Society of Greenwich continues to support local artists in town.

Cos Cob has one post office. There are two public schools in Cos Cob: Cos Cob Elementary School, 640 pupils, and Central Middle School, 740 pupils, though school boundaries cut across zip code boundaries and many students who live in Cos Cob attend other public schools in town.