Hillsborough is a census-designated place located in the center of Hillsborough Township, Somerset County, in the U.S. state of New Jersey. It was first listed as a CDP prior to the 2020 census. The CDP is in south-central Somerset County and is bordered to the northwest by Flagtown, to the west by Neshanic, and to the south by Belle Mead. U.S. Route 206 passes through the community, leading north 5 miles to Somerville, the county seat, and south 12 miles to Princeton.