Monk Gibbon was born on December 15, 1896 in Dundrum, County Dublin in Ireland, to William and Agnes (Pollock) Gibbon. He was educated at St Columba’s College in Rathfarnham, County Dublin. Gibbon won a History exhibition (scholarship) to Keble College, Oxford, but his time at Oxford was brief owing to the First World War. He served as an officer in the British Army in France. Gibbon was on leave in Dublin during the Easter Rising in 1916, and witnessed the execution of Francis Sheehy Skeffington, an event which he later reflected on in his memoir, Inglorious Soldier (1968). Gibbon was invalided out of the army in 1917, traveled and worked in Jersey, Switzerland and England, before ultimately returning to Ireland. In 1928, he married Mabel Winifred Dingwall, whom he had met while traveling in Europe.
Gibbon published several collections of poetry, including The tremulous string (1926), The branch of hawthorn tree (1927), and 17 sonnets (1932). He also published fiction, including his 1948 novel, Mount Ida, and The Pupil (1981). He knew William Butler Yeats, and is best known for his unflattering portrayal of the Irish poet in his study, The Masterpiece and the Man, Yeats as I Knew Him (1959). He was a fellow of the Royal Society of Literature and the Irish Academy of Letters. Gibbon died on October 29, 1987 in Sandycove, Dublin.