- O'KOYE
- O'YOUNG (오영)
- O.O.O
- oait
- OD
- oddeen
- oe
- off the menu (오프더메뉴)
- off the menu(오프더메뉴)
- Offing
- OFFSTORE
- ofrm (오프롬)
- OhashiTrio
- OHIORABBIT
- ohsol
- OLOGI
- Omega Sapien
- ON
- ONDA
- One By One
- One Day of the Montauk
- One Off Them
- Oneianmillion (강이안)
- ONENESS
- onthedal
- oonsoo
- OoOoot(최규철)
- OPCE
- Optical Eyez XL
- Option
- orange flavored cigarettes
- Orchid
- ORDNRYCITIZEN
- Organic Science
- ORORA (오로라)
- Otakhee
- Otis Lim
- OURTAPES
- Out Of Place (아웃 오브 플레이스)
- OVCOCO
- OXFORD DROPKICK
- Oygli