South Londonderry is an unincorporated village and census-designated place (CDP) in the town of Londonderry, Windham County, Vermont, United States. As of the 2020 census, it had a population of 147. The center of the village comprises the South Londonderry Village Historic District. The CDP is in northwestern Windham County, in the south-central part of the town of Londonderry. It sits on both sides of the West River, a southeast-flowing tributary of the Connecticut River. Vermont Route 100 passes through the community, leading north 2.5 mi to Londonderry village and south 9 mi to Jamaica.