Plattsville is a census-designated place in the towns of Easton and Fairfield, Fairfield County, Connecticut, United States. It is primarily in the town of Easton, with a portion extending south across the Mill River into Fairfield. The Merritt Parkway forms the southeast border of the CDP, and Connecticut Route 59 runs north–south through it. Plattsville was first listed as a CDP prior to the 2020 census.