Dayville is a census-designated place (CDP) in the northwest part of the town of Killingly in Windham County, Connecticut, United States.

It is located on the east side of the Fivemile River, 5 miles (8 km) north of Danielson.

Interstate 395 passes through the east side of the CDP, leading south to Norwich and north to Auburn, Massachusetts.

Dayville was first listed as a CDP prior to the 2020 census.

[2] The Dayville Historic District occupies 15 acres (6.1 ha) at the center of the village.