| Name | Functions  | Event Dates | Events | Resources | ||
|---|---|---|---|---|---|---|
| Sean O'Riada | Composer | 1961 | 1 | |||
| Bettina Ostermeier | Composer | 2011 | 1 | |||
| Anders Ortman | Composer | 2020 | 5 | |||
| Bruce Odland | Composer | 2013 | 1 | |||
| Thodoris Oikonomou | Composer, Musician | 2007 - 2020 | 2 | |||
| Cristian Oroșanu | Conductor | 2012 | 1 | |||
| Stelian Olariu | Conductor | 2007 | 1 | |||
| Vladimir Ovodok | Conductor | 2020 | 1 | |||
| Kathrine Ogletree | Costume Designer | 2003 | 1 | |||
| César Olivar | Costume Designer | 2004 | 1 | 1 | ||
| Leni Osswald | Costume Designer | 1955 - 1962 | 2 | |||
| Juliet Ouyoung | Costume Designer | 1993 | 1 | |||
| Joan O'Clery | Costume Designer | 2000 - 2013 | 6 | 1 | ||
| Lillian Olsen | Costume Designer | 2000 | 7 | |||
| Cathrine Gåre Opstad | Costume Designer | 2005 - 2008 | 90 | |||
| Paul Owen | Costume Designer | 1972 | 1 | |||
| Brian O’Keefe | Costume Designer | 2009 | 1 | |||
| L'ubica Obuchová | Costume Designer | 1985 | 1 | 1 | ||
| Ulrike Obermüller | Costume Designer | 1991 - 2016 | 2 | |||
| Michael Olich | Costume Designer | 1992 | 1 | |||
| Peter O’Brien | Costume Designer | 2015 | 1 | |||
| Kikuko Ogata | Costume Designer | 1968 - 2010 | 2 | |||
| Klára Oltványi | Costume Designer | 2005 | 1 | |||
| Janel Opeka | Costume Designer | 2003 | 1 | |||
| Marette Oppenberg | Costume Designer | 2003 | 2 | 1 | ||
| Anna Oliver | Costume Designer | 1999 - 2010 | 3 | |||
| Anna Nuka Olsen Rosing | Costume Designer | 2005 | 1 | |||
| Ninna Olesen | Costume Designer | 2008 | 1 | |||
| Elena Ju. Orlova | Costume Designer | 2008 - 2011 | 2 | |||
| Dana Osborne | Costume Designer | 2011 | 1 | |||
| Oliver Olsen | Costume Designer | 1959 | 2 | |||
| Hiram Alexander Orozco | Costume Designer | 2016 | 1 | |||
| - Owen-Maclean | Costume Designer | 1950 | 1 | |||
| Cachi Otero | Costume Designer | 1971 | 3 | |||
| Carol Oditz | Costume Designer | 1981 | 1 | |||
| Penn O'Gara | Costume Designer | 2019 | 1 | |||
| Sarah M. Oliver | Costume Designer | 2019 | 1 | |||
| Lujo Obendorf | Costume Designer | 1952 | 1 | |||
| Tracy Oleinick | Costume Designer | 1 | ||||
| Joan O’Clery | Costume Designer | 2023 | 1 | |||
| Valeria Onnis | Costume Designer | 2012 | 2 | |||
| Uwe Oelkers | Costume Designer, Designer | 1985 - 2010 | 7 | |||