Colum was born in Longford, where his father was workhouse master, on 8 December 1881. At seventeen he became a clerk in the Irish Railway Clearing House in Dublin, but left in 1904 determined to make a living through writing. His first poems appeared in The United Irishman, edited by Arthur Griffith. The Saxon Shillin' (1902) won a competition for a play to discourage young Irishmen from joining the British army.

Colum acted with the new Irish National Theatre Society, but after his play Broken Soil was staged in 1903, he concentrated on writing. He was one of the founders of the Abbey Theatre, where his realistic peasant drama The Land (1905) was an early success. Thomas Muskerry (1910) was also staged by the Abbey, but thereafter Colum failed to fulfil his early promise as a dramatist.

His first book of verse, Wild Earth, appeared in 1907, with lyric poems like 'The Plougher', 'A Drover' and 'An Old Woman of the Roads'. He married in 1912, and in 1914 the Colums sailed to America, soon entering New York literary circles. Colum began to write children's stories for the Sunday Tribune, which led to a collection, TheKing of lreland's Son (1916), followed over theyears by the many children's books which overshadowed his other work. New poems appeared in an American edition of Wild Earth (1916), including tlhe popular 'She Moved Through the Fair'.

In 1922 the Hawaiian legislature commissioned Colum to write for children the islands' folklore, three volumes resulting from his visit. A book of verse, Dramatic Legends (1922), was followed by his first novel, Castle Conquer (1923), set in an impoverished nineteenth century, as was The Flying Swans (1937). Of the later collections of verse, Irish Elegies (1958) is interesting for its portraits of Roger Casement, Griffith, James Joyce and others.

The Colums lived in France in the early 1930s, Colum renewing an old friendship with Joyce, for whom he typed parts of Finnegans Wake. On returning to America, they both taught comparative literature at Columbia University, becoming US citizens in 1945.When Mary Colum died in 1957, Colum completed their anecdotal Our Friend James Joyce (1958). In 1959 he published Ourselves Alone, a biography of Griffith begun many years earlier. Colum died in Enfield, Connecticut, on 11 January 1972.