Penns Neck is an unincorporated community located within West Windsor Township in Mercer County, New Jersey, United States. The community developed at the intersection of the Trenton-New Brunswick Turnpike (now U.S. Route 1) and Washington Road. The Penns Neck Circle and the historic Penns Neck Baptist Church (1812) are both located in Penns Neck. The Princeton Branch rail line, known as the Dinky, has run through the area since 1865, and stopped at Penns Neck station until January 1971.