Seabrook is a town in Rockingham County, New Hampshire, United States. The population was 8,401 at the 2020 census. Located at the southern end of the coast of New Hampshire, on the border with Massachusetts, Seabrook is noted as the location of the Seabrook Station Nuclear Power Plant, the third-most recently constructed nuclear power plant in the United States. Seabrook is the first town one encounters when entering New Hampshire northbound on I–95.