Mag Trega: Moytra, in the County Longford
Mag Tuaga: a plain in Mayo
Maic Miled: the Milesians
Mairg: a district in which is Slievemargie, in the Queen's County and the County Kilkenny
Manannan: son of Ler, a fairy god
Margine: a place in Cualnge
Mas na Righna: Massareene, in the County Antrim
Mata Murisc: mother of Ailill
Medb: queen of Connacht and wife of Ailill (pronounced Mave; in modern Connacht Irish Mow to rhyme with cow)