Desertmartin (locally [ˈdɛzərtˈmartn],from Irish Díseart Máirtín, meaning "hermitage of St. Martin") is a small village in County Londonderry, Northern Ireland. It is four miles from Magherafelt, at the foot of Slieve Gallion. In the 2001 Census Desertmartin greater area had a population of 1,276. It had a population of 2257 in 1837 and 3101 in 1910. It lies within Desertmartin parish, Magherafelt District Council, and the historic barony of Loughinsholin. Neighbouring settlements include Draperstown, Magherafelt, Moneymore, and Tobermore.
When County Coleraine was created in 1585, its administration was meant to be carried out in the town of Coleraine. However, the jail and courthouse were built in Desertmartin, the middle of the Barony of Loughinsholin, which then lay in neighbouring County Tyrone. After the Flight of the Earls the escheated land was transferred to County Coleraine. The enlarged county was renamed County Londonderry.
Desertmartin (from Irish Díseart Mhartain, meaning "hermitage of St. Martin") is a civil and ecclesiastical parish in County Londonderry, Northern Ireland. Containing one major settlement, Desertmartin, it is bordered by the civil parishes of Ballynascreen, Desertlyn, Kilcronaghan, Lissan, Maghera, and Magherafelt. It lies within the former barony of Loughinsholin and is situated in Magherafelt District Council. As a Church of Ireland parish it is within the Diocese of Derry and Raphoe.
The parish of Desertmartin lies at the foot of Slieve Gallion, on the easternmost limit of the Sperrin Mountains range. Slieve Gallion rises to an elevation of 1,730 feet (530 m) and is near the south-western boundary of the parish. The rest of the parish is comparatively low averaging around 270 feet (82 m) above sea level, and in its easterly descent from Slieve Gallion is broken by small glens and ravines, such as; Reuben's, Gortanewry, and Quilly.
The main hills in the parish are; Slieve Gallion Cairn, 1,625 feet (495 m) high; Brackamore Hill, 418 feet (127 m) high; Windy Castle, 1,216 feet (371 m) high; Tirgan Rock, 590 feet (180 m) high.