- Orkan Władysław
- Orkhon Province
- Orkney Islands
- Orlande de Lassus
- Orlando
- Orlando Gibbons
- Orlando Museum of Art
- Orlando Winfield Wilson
- Orlicz
- Orlicz class
- Orlicz-Lorentz space
- Orlicz norm
- Orlicz-Pettis theorem
- Orlicz space
- or, Life in the Woods
- Orlov crater
- orlov trotter
- Orly Castel-Bloom
- ORM
- Ormoc Bay
- Ormosia hosiei in Ya’an City
- Orn
- ornamenal water plant
- ornamental animal
- ornamental aqualife