| Abbreviation | Definition |
|---|---|
| OAT | Optometry Admission Test |
| OAU | Obafemi Awolowo University |
| OAU | Observatorios Ambientales Urbanos |
| OAU | Of the Awolowo University |
| OAU | Omdurman Ahlia University |
| OAU-IFE | Obafemi Awolowo University,Ile-Ife |
| OBI | Oklahoma Blood Institute |
| OBI | Oneida Baptist Institute |
| OBI | Osaka Bioscience Institute |
| OBIR | Organizational Behavior and Industrial Relations |
| OBR | Ohio Board of Regents |
| OBS | Observatory |
| OBU | Oklahoma Baptist University |
| OBU | Ouachita Baptist University |
| OC | Off Campus |
| OC | Oklahoma Christian |
| OC | Online Class |
| OC | Open Concepts |
| OCAD | OCAD University |
| OCADU | OCAD University (prior to 2010, OCAD was an acronym for Ontario Collage of Art Design) |