This is a sub-list from List of doping cases in sport representing a full list of surnames starting with O.
| Name | Country | Event | Banned substance(s) | Reference(s) | |
|---|---|---|---|---|---|
| Kirk O'Bee |
 United States
|
Cycling | Testosterone | ||
| Chiedozie Offiah |
 United Kingdom
|
Basketball | Test tampering | ||
| Stuart O'Grady |
 Australia
|
Cycling | EPO (Self admit) | ||
| Reza Ojagh |
 Iran
|
Swimming | Nandrolone | ||
| Mirela Olczak |
 Poland
|
Swimming | Methylhexaneamine | ||
| Olena Olefirenko |
 Ukraine
|
Rowing | |||
| Ruslan Oleksenko |
Ukraine
|
Wrestling | THC | ||
| Andrey Oleynik |
Ukraine
|
Swimming | Cannabis | ||
| Jacques Oliger |
 Chile
|
Weightlifting | |||
| Achiliev Olimbeck |
 United Arab Emirates
|
Weightlifting | Metandienone | ||
| Victor Felipe Silveira Oliveira |
 Brazil
|
Volleyball | Steroids | ||
| Larry Olubamiwu |
United Kingdom
|
Boxing | |||
| Naiij Omid |
Iran
|
Weightlifting | Metandienone | ||
| Esther Omosehin |
 Nigeria
|
Swimming | Ephedrine | ||
| Nathan O'Neill |
Australia
|
Cycling | Phentermine | ||
| Elizabeth Onuah |
Nigeria
|
Weightlifting | Hydrochlorothiazide, Amiloride | ||
| Oo Mya Sanda |
 Myanmar
|
Weightlifting | Metabolite | ||
| Niusila Opeloge |
 Samoa
|
Weightlifting | |||
| Omar Ortiz |
 Mexico
|
Football (soccer) | Oxymetholone, masteron | ||
| Michal Orzechowski |
Poland
|
Wrestling | THC | ||
| Ronnie O'Sullivan |
 England
|
Snooker | Cannabis | ||
| Bilal Othman |
 Syria
|
Weightlifting | |||
| Bilikis Otunla |
Nigeria
|
Weightlifting | Nandrolone | ||
| Abdelkrim Ouakali |
 Algeria
|
Wrestling | Furosemide | ||
| Ouyang Kunpeng |
 China
|
Swimming | Clenbuterol | ||
| Artem Ovechkin |
 Russia
|
Cycling | |||
| Alistair Overeem |
 Netherlands
|
MMA and Kickboxing | Testosterone- Epitestosterone | ||
| Mita Overvliet |
Netherlands
|
Weightlifting | Norandrosterone, Furosemide |