All Anime List "o" at Gogoanime
- One Punch Man 2nd Season
- One Punch Man 2nd Season Commemorative Special
- One Punch Man 2nd Season Specials
- One Punch Man Specials
- One Punch Man: Road to Hero
- One Room
- One Room Second Season
- One Room Second Season Special
- One Room Third Season
- One: Kagayaku Kisetsu e
- Oneechan ga Kita
- Onegai My Melody
- Onegai My Melody: Kuru Kuru Shuffle!
- On-Gaku: Our Sound
- Onigiri
- OniAi
- OniAi Specials
- Onimai: I'm Now Your Sister!
- Onimai: I'm Now Your Sister! (Uncensored)
- Ogre Slayer
- Onimusha
- Onipan!
- Onmyouji
- Onyankopon
- Okami-San and Her Seven Companions
- Oomuro-ke: Dear Sisters
- Oomuro-ke: Dear Friends
- Ōoku: The Inner Chambers
- Ooya-san wa Shishunki!
- Opus.COLORs
- Orange
- Orange: Mirai
- Ore ga Ojousama Gakkou ni "Shomin Sample" Toshite Gets♥Sareta Ken Specials
- Ore ga Suki nano wa Imouto dakedo Imouto ja Nai Specials
- Oreshura
- Ore no Nounai Sentakushi ga, Gakuen Love Comedy wo Zenryoku de Jama Shiteiru OVA