Tóibín was born in 1955 in Enniscorthy, County Wexford, in the southeast of Ireland. Tóibín's parents were Bríd and Michael Tóibín. He is the second youngest of five children. His grandfather, Patrick Tobin, was a member of the IRA, as was his grand-uncle Michael Tobin. Patrick Tobin took part in the 1916 Rebellion in Enniscorthy and was subsequently interned in Frongoch in Wales. Tóibín's father was a teacher who was involved in the Fianna Fáil party in Enniscorthy; he died when Colm was 12 years old.