- OASE - Self-help and Communication Centre
- Occupational Counselling - Career Service
- Office for Admission and Registration
- Office of Co-operation between the Ruhr-Universität Bochum - Industrial Metal Union
- Offices of the Rectorate and the Chancellor
- Official Seal
- Online-Enrolment
- Online-Test Study Counselling - BORAKEL
- OPAC - Online Public Access Catalogue
- Open Day
- Organ (Klais-Organ in Audi max)
- Organ Concerts
- Oriental and Islamic Studies
