Lempster is a town in Sullivan County, New Hampshire, United States. Settlements include the town center (Lempster village) and the village of East Lempster. First granted by colonial governor Jonathan Belcher in 1735 as Number 9, it was re-granted in 1753 as Dupplin, after Scottish lord Thomas Hay, Viscount Dupplin, by Governor Benning Wentworth. The town was re-granted one final time in 1767 as Lempster, after one of the titles of a Sir Thomas Farmer of Lempster and incorporated in 1772.