Forrest Reid was born in Belfast and was educated at the Royal Belfast Academical Institution and Christ's College, Cambridge, where he read medieval and modern languages.
He returned to Belfast and lived there for the rest of his life. He was a friend of E. M. Forster.He also published criticism of W. B. Yeats and Walter de la Mare, as well as Illustrators of the Sixties, a study of Victorian woodcut artists.
He published articles in many magazines, including the Westminster Review and the Ulster Review, and he reviewed books for the Manchester Guardian. Apostate, an autobiography, was published in 1926, and its sequel, Private Road, was published in 1940.
He was a founder member of the Irish Academy of Letters.
Reid's writing centre on the world of boys, and are permeated by the quest for the ideal playmate friend. The celebration of a Greek ideal of male friendship in his works placed Reid's characters in a pagan, lyrical world.
He died at Warrenpoint, County Down.
His romantic and mystical novels includes The Kingdon of Twilight (1904), The Garden God: a Tale of Two Boys (1905), Following Darkness (1913), and a trilogy published with the title Tom Barber: Uncle Stephen (1931), The Retreat (1934), and Young Tom (1944) which won the James Tait Black Memorial Prize. He also wrote two autobiographies, Apostate (1926), and Private Road (1940).