Thompson is a town in Windham County, Connecticut, United States. The town is part of the Northeastern Connecticut Planning Region. The town was named after Sir Robert Thompson, an English landholder. The population was 9,189 at the 2020 census. Thompson is located in the northeastern corner of the state and is bordered on the north by Webster, Massachusetts and Dudley, Massachusetts, on the east by Douglas, Massachusetts and Burrillville, Rhode Island, on the west by Woodstock, Connecticut, and on the south by Putnam, Connecticut.

Windham County is one of the eight historical counties in the U.S. state of Connecticut, located in its northeastern corner. As of the 2020 census, the population was 116,418, making it the least populous county in Connecticut. It forms the core of the region known as the Quiet Corner. Windham County is included in the Worcester, MA-CT Metropolitan Statistical Area, which is also included in the Boston-Worcester-Providence, MA-RI-NH-CT Combined Statistical Area. The entire county is within the Quinebaug and Shetucket Rivers Valley National Heritage Corridor, as designated by the National Park Service.