- Oregon grape
- Oregon Health Sciences University
- Oregon holly grape
- Oregon Institute of Technology
- Oregon myrtle
- Oregon pine
- Oregon Polytechnic Institute
- Oregon State University
- Oregon Trail
- oreide
- oreide
- Orekhovo-Zuyevo
- Orel
- Orem
- Orenburg
- Orense
- oreodont
- oreodonts
- ores
- Orestes
- Oresund
- Orff
- or foredone
- orfray
- orfray