Anime & Game Series Beginning with O
- [Oshi no ko]
- Curious George
- My Next Life as a Villainess: All Routes Lead to Doom!
- Obey Me!
- Occultic;Nine
- Octave
- OCTOPATH TRAVELER
- Oda Nobuna no Yabou
- Odd Taxi
- Oh-oku ( Danjo Gyakuten)
- Oishinbo
- Ojamajo
- Okami Kakushi
- Okami to Koshinryo (Wolf and Spice)
- Okasan to Issho
- Okiku Furikabutte
- Olympia Cuculus
- Omamori Himari
- Omoi, Omoware, Furi, Furare
- Omoide no Marnie (When Marnie Was There)
- One Off
- One Piece
- One Punch Man
- Onegai Teacher (Please Teacher!)
- Ongaku to Hito
- ONGEKI
- Onigiri
- Onihei Hankacho
- Onimusha
- Online Game
- Only Yesterday
- Onsen Yosei Hakone-Chan
- Ookami kodomo no Ame to Yuki (Wolf Children)
- Opus.COLORs
- Ordian
- Ore Ga Sukina No Ha Imotodakedo Imoto Janai
- Ore monogatari!!
- Ore no Imoto ga Kon nani Kawaii wake ga nai
- Ore no Kanojo to Osananajimi ga Shuraba Sugiru
- Ore no nonai sentakushi ga gakuen Love comedy wo Zenryoku de Jyama Shiteiru
- Ore o Suki nano wa Omae dake kayo
- Ore, Twintail ni Narimasu.
- Oretachin ni Tsubasa wa Nai
- Orient
- Osama Ranking
- Osananajimi ga zettai ni makenai love-come
- Oshi ga Budokan Ittekuretara Shinu
- Osomatsu-san
- Ossan's Love
- Otaku ni Koi wa Muzukashii
- Otogi Jushi Akazukin
- Otome continue
- Otome wa Boku ni Koishiteru
- Otome Yokai Zakuro
- Otona Anime
- Ouran Koko Host Club
- Outbreak Company
- Overlord
- Overman King-Gainer
- Overtake!
- Seraph of the End
- Shomin Sample
- The Royal Tutor (Oshitsu Kyoshi Haine)
- Uncle from Another World