List of composers / O
If
- Karola Obermüller (* 1977)
- Carl Oberthür (1819–1895)
- Jana Obravská (1930–1987)
- Jacob Obrecht (around 1457 / 58–1505)
- Nikolai Borissowitsch Obuchow (1892–1954)
Oc
- Turlough O'Carolan (1670-1738)
- Siegfried Ochs (1858–1929)
- Andrej Očenáš (1911–1995)
- Sebastian Ochsenkhun (1521–1574)
- Johannes Ockeghem (around 1410 / 20–1497)
- Matthias Ockert (* 1970)
Oe
- Helmut Oehring (* 1961)
- Anne-Marie Ørbeck (1911–1996)
Of
- Jacques Offenbach (1819–1880)
Above
- Edgar Oganessjan (1930–1998)
- John Ogdon (1937-1989)
- Claus Ogermann (* 1930)
- Domenico Dall'Oglio (1700–1764)
Oh
- Maurice Ohana (1913–1992)
OK
- German Okunew (1931–1973)
Oil
- Marguerite Olagnier (1844–1906)
- Tiberiu Olah (1928-2002)
- Franz Martin Olbrisch (* 1952)
- Juan Manuel Olivares (around 1760 to around 1797)
- Vivienne Olive (* 1950)
- Jocy de Oliveira (* 1936)
- John Oliver (born 1959)
- Pauline Oliveros (1932-2016)
On
- George Onslow (1784-1853)
Op
- Henryk Opieński (1870–1942)
- Franco Oppo (1935-2016)
Or
- Julián Orbón (1925–1991)
- Joaquín Orellana (* 1930/37)
- Carl Orff (1895–1982)
- Hannibal Orgas (around 1575 - 1629)
- Vincenzo Orgitano (around 1735 to around 1807)
- Giuseppe Maria Orlandini (1676–1760)
- Alessandro Orologio (around 1550 - 1633)
- Leo Ornstein (1892-2002)
- Johann Georg Orschler (1698–1767)
- Robin Orr (1909-2006)
- Juan Orrego-Salas (1919-2019)
- Diego Ortiz (around 1510 - around 1570)
- Gabriela Ortiz (* 1964)
- Marbriano de Orto (around 1460 - 1529)
Os
- Klaus Ospald (* 1956)
- Slavko Osterc (1895–1941)
- Otakar Ostrčil (1879–1935)
- Andreas Oswald (1634-1665)
- Henrique Oswald (1852-1931)
- James Oswald (around 1710–1769)
Ot
- Hisatada Otaka (1911-1951)
- Caspar Othmayr (1515–1553)
- Daniel Ott (* 1960)
- Bernardo Ottani (1736-1827)
- Hans Otte (1926-2007)
- Franz Joseph Otter (1760-1836)
- Ernst Julius Otto (1804–1877)
- Valerius Otto (1579-after 1612)
Ou
- Frederick Ouseley (1825-1889)
Ow
- Vyacheslav Ovchinnikov (1936-2019)
Oz
- Étienne Ozi (1754-1813)