Born in Dublin in 1952, Liam Mac Cóil lives in the Gaeltacht of Ráth Cairn, County Meath.
He is presently co-editor of the literary annual Bliainiris and director of the publishing house Carbad.
Early in his career, he published two translations from the Welsh, Tiocfaidh Lá (original title: Daw Dydd, a selection of writings by Welsh-language activist Ffred Ffransis) and Saibhreas Chnoic Chaspair (Trysor Bryniau Caspar, a young-adult novel by John Selwyn Lloyd).
In 2010 he published a work of personal reflections on the composer Charles Villiers Stanford titled An Chláirseach agus an Choróin.
His third novel, Fontenoy, won the Gradam Uí Shúilleabháin (an annual prize for Irish-language books) in 2006.