John Millard Dunn (5 January 1865 – 3 March 1936) was organist and choirmaster for St. Peter's Cathedral, Adelaide for 44 years.
John Dunn was born in North Adelaide a twin son of John Charles Dunn and his wife Lydia Charlotte Dunn née Smithson, of Barnard Street, North Adelaide. He was educated at John Whinham's North Adelaide Grammar School, and studied piano under Miss Francis of Glenelg, then E. Smith-Hall and Herr Boehm. He was a choirboy at St. Peter's Cathedral under Arthur Boult, and was frequently a featured soloist. He also studied organ under Mr. Boult and displayed such proficiency that in 1882 he became his assistant. He had secured full-time positions with Francis Clark & Sons and the Bank of Australasia, but in 1888 he sailed for London to study with W. de Manby Sergison, organist at St. Peter's, Eaton square, London, then in 1889 he furthered his studies under Sir Frederick Bridge, the great Westminster Abbey organist. On his return to Adelaide he took up teaching at the Adelaide College of Music (later Elder Conservatorium) under Cecil Sharp and I. G. Reimann. He was appointed organist to the Cathedral on 1 November 1891, and officiated at the inauguration of the new organ in 1930; the last service at which he presided was just a week before his death at the age of 71 years.
He served as conductor for the Adelaide Orpheus Society and president of the Adelaide Society of Organists.
He was the composer for a stage musical The Mandarin with libretti by Harry Congreve Evans, performed at the Theatre Royal, Adelaide in 1896.
Dunn was a successful teacher of the organ: two students of whom he was particularly proud were Arthur H. Otto, who on occasion filled in as assistant; and Horace Weber, Cathedral organist at Napier, New Zealand.
He taught music theory at Tormore House, a school for girls at North Adelaide.