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.

Rockingham County is a county in the U.S. state of New Hampshire. As of the 2020 census, the population was 314,176, making it New Hampshire's second-most populous county. The county seat is Brentwood. Rockingham County is part of the Boston-Cambridge-Newton, MA-NH Metropolitan Statistical Area and the greater Boston-Worcester-Providence, MA-RI-NH-CT Combined Statistical Area. Per the 2020 census, it was New Hampshire's fastest growing county from 2010 to 2020.