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. The more densely settled portion of town, where 11,645 people lived at the 2020 census, is defined as the Londonderry census-designated place (CDP) and roughly occupies the southeastern and southern parts of town, around New Hampshire Route 102.