Londonderry is a town in western Rockingham County, New Hampshire, United States. It sits between Manchester and Derry, the largest and fourth-largest communities in the state. The population was 25,826 at the 2020 census. Londonderry is known for its apple orchards and is home to the headquarters of Stonyfield Farm and part of Manchester–Boston Regional Airport.

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.