| Gaelic form | Mac Giolla Martain |
| Meaning | Son of the devotee of Saint Martin — giolla (devotee, servant) + Martain (Martin), referring to the founder of monasticism in Gaul |
| Province | Connacht |
| Core counties | Roscommon (primary), Sligo, Mayo |
| Variant spellings | Gilmartin, Gilmartain, MacGilmartin, Kilmartin |
Gilmartin is the anglicised form of Mac Giolla Martain, meaning son of the devotee of Saint Martin. The element giolla (variously anglicised as Gil-, Kil-, or -ly) was used in Irish names to denote a devoted follower or servant of a particular saint. Martin here refers to Saint Martin of Tours (c.316–397), the soldier-turned-bishop who became one of the most popular saints in western Christendom. His feast day — 11 November — is Martinmas, which was observed across Ireland.
Names beginning with Mac Giolla — devotee surnames — are particularly concentrated in the north and west of Ireland, where the cult of particular saints was especially strong. The Connacht Gilmartins, based in Roscommon and Sligo, were a sept who traced their descent through a common ancestor who bore the devotee-name of Saint Martin.
County Roscommon holds the primary concentration of Gilmartin families. The barony of Boyle in north Roscommon, bordering Sligo, is particularly associated with the name. Roscommon, the heartland of the ancient O'Connor kings of Connacht, was a county with a deep Gaelic tradition, and the Gilmartins were part of this world as a recognised sept with their own territory within the broader Connacht order.
County Sligo, immediately north of Roscommon, holds the second concentration of Gilmartin families. North Roscommon and south Sligo form a connected region — the border between them runs through territory that was, in Gaelic times, part of a continuous cultural and political zone. Sligo Gilmartins appear in records from the seventeenth century onwards.
West of Roscommon, County Mayo also has Gilmartin families, reflecting the spread of the sept from its core territory into the neighbouring county. East Mayo shares the cultural world of Roscommon, and Gilmartin families appear in the eastern baronies of Mayo bordering Roscommon.
The Mac Giolla Martain sept were part of the larger world of the O'Connor kings of Connacht, who dominated the western province for centuries and provided two High Kings of Ireland — Turlough O'Connor and his son Rory, the last High King. Like other Connacht septs, the Gilmartins operated within this overlordship, providing military service and loyalty in exchange for protection and land-holding rights.
Connacht proved more resistant to Norman penetration than Leinster or Munster. The de Burgos (later Burkes) established a major presence, but large parts of the province remained under Gaelic Irish control through the medieval period. The Gilmartins, in north Roscommon and Sligo, were in territory that remained substantially Gaelic in character through the fifteenth century.
The Cromwellian settlement disrupted the Connacht Gaelic order as thoroughly as it had disrupted Leinster and Munster. The transplantation policy brought Catholic landowners from other provinces into Connacht while simultaneously displacing Connacht families from better land to poorer holdings. Gilmartin families survived this period as farming families, having lost whatever lordly status their ancestors may have held.
Gilmartin is a less common Irish surname in the diaspora than many, reflecting its concentrated distribution in a single region of north Connacht. Irish-American Gilmartins appear primarily in the northeast cities — New York, Boston — and in cities with significant Connacht Irish populations such as Chicago. Britain (particularly Liverpool and Manchester) received Roscommon and Sligo emigrants in large numbers, and Gilmartin is established in those communities.
Gilmartin research should focus on north County Roscommon and south County Sligo. The Roscommon County Library and Sligo County Library both hold local historical collections. IrishGenealogy.ie covers civil and Catholic parish records for both counties. Griffith's Valuation shows Gilmartin households concentrated in the Boyle barony of north Roscommon and in south Sligo.
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