Ipswich River is a small river in northeastern Massachusetts, United States. It held significant importance in early colonial migrations inland from the ocean port of Ipswich. The river provided safe harborage at offshore Plum Island Sound to early Massachusetts subsistence farmers, who were also fishermen. A part of the river forms town boundaries and divides Essex County, Massachusetts on the coast from the more inland Middlesex County. It is long, and its watershed is approximately , with an estimated population in the area of 160,000 people.