controversial Anglican bishop of Birmingham, a leader in the Church of England modernist movement.

Barnes was educated at Trinity College, Cambridge, where he subsequently became fellow, lecturer in mathematics, and tutor. He was ordained in 1903. By 1915, when he was made master of the Temple, he had established a reputation for outspoken and provocative preaching, which he maintained as canon of Westminster (1918–24). Appointed bishop of Birmingham in 1924 on the recommendation of the prime minister, Ramsay MacDonald, he immediately attacked ritualistic practices and in 1929 evoked much protest by his refusal to install an Anglo-Catholic priest.

Barnes's scientific approach to Christian dogma (exemplified in his Gifford lectures on Scientific Theory and Religion 【1933】) brought him into open conflict with his fellow bishops; his controversial The Rise of Christianity (1947) was condemned by the archbishops of Canterbury and York. An uncompromising pacifist, he refused during World War II to take part in national days of prayer and later vigorously opposed German rearmament and the use of the atomic bomb.