| O'Clery, Joan | Joan O'Clery | Costume Designer | 2000 - 2013 | 6 | 1 |
| Olsen, Lillian | Lillian Olsen | Costume Designer | 2000 | 7 | |
| Opstad, Cathrine Gåre | Cathrine Gåre Opstad | Costume Designer | 2005 - 2008 | 90 | |
| Owen, Paul | Paul Owen | Costume Designer | 1972 | 1 | |
| O’Keefe, Brian | Brian O’Keefe | Costume Designer | 2009 | 1 | |
| Obuchová, L'ubica | L'ubica Obuchová | Costume Designer | 1985 | 1 | 1 |
| Obermüller, Ulrike | Ulrike Obermüller | Costume Designer | 1991 - 2016 | 2 | |
| Olich, Michael | Michael Olich | Costume Designer | 1992 | 1 | |
| O’Brien, Peter | Peter O’Brien | Costume Designer | 2015 | 1 | |
| Ogata, Kikuko | Kikuko Ogata | Costume Designer | 1968 - 2010 | 2 | |
| Oltványi, Klára | Klára Oltványi | Costume Designer | 2005 | 1 | |
| Opeka, Janel | Janel Opeka | Costume Designer | 2003 | 1 | |
| Oppenberg, Marette | Marette Oppenberg | Costume Designer | 2003 | 2 | 1 |
| Oliver, Anna | Anna Oliver | Costume Designer | 1999 - 2010 | 3 | |
| Olsen Rosing, Anna Nuka | Anna Nuka Olsen Rosing | Costume Designer | 2005 | 1 | |
| Olesen, Ninna | Ninna Olesen | Costume Designer | 2008 | 1 | |
| Orlova, Elena, Ju. | Elena Ju. Orlova | Costume Designer | 2008 - 2011 | 2 | |
| Osborne, Dana | Dana Osborne | Costume Designer | 2011 | 1 | |
| Olsen, Oliver | Oliver Olsen | Costume Designer | 1959 | 2 | |
| Orozco, Hiram Alexander | Hiram Alexander Orozco | Costume Designer | 2016 | 1 | |
| Owen-Maclean, - | - Owen-Maclean | Costume Designer | 1950 | 1 | |
| Otero, Cachi | Cachi Otero | Costume Designer | 1971 | 3 | |
| Oditz, Carol | Carol Oditz | Costume Designer | 1981 | 1 | |
| O'Gara, Penn | Penn O'Gara | Costume Designer | 2019 | 1 | |
| Oliver, Sarah, M. | Sarah M. Oliver | Costume Designer | 2019 | 1 | |
| Obendorf, Lujo | Lujo Obendorf | Costume Designer | 1952 | 1 | |
| Oleinick, Tracy | Tracy Oleinick | Costume Designer | | 1 | |
| O’Clery, Joan | Joan O’Clery | Costume Designer | 2023 | 1 | |
| Oelkers, Uwe | Uwe Oelkers | Costume Designer, Designer | 1985 - 2010 | 7 | |
| Ohland, Hans | Hans Ohland | Costume Designer, Designer | 1963 - 1981 | 4 | |
| Ojamaa, Pekka | Pekka Ojamaa | Costume Designer, Designer | 1990 - 2001 | 9 | |
| O'Brien, Timothy | Timothy O'Brien | Costume Designer, Designer | 1964 - 1996 | 12 | |
| Olsen, Thale Kvam | Thale Kvam Olsen | Costume Designer, Designer | 2013 | 4 | |
| Oechslin, Ary | Ary Oechslin | Costume Designer, Designer | 1952 - 1978 | 11 | 1 |
| Oskam, Peter | Peter Oskam | Costume Designer, Designer | 1985 | 2 | |
| Oberle, Carl-Friedrich | Carl-Friedrich Oberle | Costume Designer, Designer | 1994 | 2 | |
| O'Malley, Geraldine | Geraldine O'Malley | Costume Designer, Designer | 1989 - 1990 | 4 | |
| Olsson, Marie | Marie Olsson | Costume Designer, Designer | 2014 | 2 | |
| Oxlade, Jonathon | Jonathon Oxlade | Costume Designer, Designer | 2007 | 2 | 1 |
| Otto, Frank-Tilmann | Frank-Tilmann Otto | Costume Designer, Designer | 2008 | 4 | |
| Oseng, Ellen | Ellen Oseng | Costume Designer, Designer | 2009 | 2 | |
| Ollila, Yrjö | Yrjö Ollila | Costume Designer, Designer | 1930 | 2 | |
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