Grafton is a town in Worcester County, Massachusetts, United States. The population was 19,664 at the 2020 census. The town consists of the North Grafton, Grafton, and South Grafton geographic areas, each with a separate ZIP Code. Incorporated in 1735, the town is home to a Nipmuc village known as Hassanamisco Reservation, the Willard House and Clock Museum, Community Harvest Project, and the Tufts University Cummings School of Veterinary Medicine. Grafton operates the state's largest on-call fire department, with 74 members.

Worcester County is a county in the U.S. state of Massachusetts. At the 2020 census, the population was 862,111, making it the second-most populous county in Massachusetts. It is also the largest county in Massachusetts by geographic area. The largest city and traditional shire town is Worcester. Worcester County is part of the Worcester, MA–CT metropolitan statistical area and the Boston-Worcester-Providence combined statistical area.