Series Beginning with O
- [Oshi no ko]
- Curious George
- My Next Life as a Villainess: All Routes Lead to Doom!
- Ochoyan
- OCTOPATH TRAVELER
- Odd Taxi
- Odoru Daisosasen Series
- Oh-oku ( Danjo Gyakuten)
- Ohoka Echizen
- Oi! Hanimaru
- Oishinbo
- Ojarumaru
- Okaeri Mone
- Okasan to Issho
- One Piece
- One Punch Man
- Onegai My Melody
- Onihei Hankacho
- Onimusha
- Online Game
- Only Mercedes
- Only Yesterday
- Onna Joshu Naotora
- Onsen Musume
- Ookami kodomo no Ame to Yuki (Wolf Children)
- Orange Page
- Ore no Imoto ga Kon nani Kawaii wake ga nai
- Ore no Sora Series
- Oretachi Majikou Destroy
- Orix Buffaloes
- Osama Game
- Oshigoto Danshi
- Osomatsu-san
- Ossan's Love
- Otacool
- Otoko wa Tsuraiyo
- Otome continue
- Otome Yokai Zakuro
- Otona Anime
- Otona no Kagaku Magazine
- Otona No Nurie
- Otona no Oshare Techo
- Ouran Koko Host Club
- Owarai Danshiko
- Seraph of the End
- The Royal Tutor (Oshitsu Kyoshi Haine)