Colchester is a town in Chittenden County, Vermont, United States. As of the 2020 census, the population of Colchester was 17,524. It is the third-most populous municipality and most populous town in the state of Vermont. Colchester borders Burlington, Vermont's most populous municipality. The town is directly to Burlington's north on the eastern shore of Lake Champlain, to the west of the Green Mountains. The Vermont National Guard is based in the town, and it is also home to Saint Michael's College and the Vermont campus of Southern New Hampshire University.

Chittenden County is the most populous county in the U.S. state of Vermont. As of the 2020 census, its population was 168,323. The county seat is Vermont's most populous municipality, the city of Burlington. The county has over a quarter of Vermont's population and more than twice the population of Vermont's second-most populous county, Rutland. The county also has more than twice the population density of Vermont's second-most dense county, Washington. The county is named for Vermont's first governor and one of the framers of its constitution as an independent republic and later U.S. state, Thomas Chittenden.