- One Week Friends Kaori no Nikki
- Onee-chan ga Kita
- Onegai My Melody
- Onegai My Melody: Kuru Kuru Shuffle!
- Onegai Teacher
- Onegai Twins
- Onegai Twins
- Onegai Twins EP OVA
- Onegai☆Teacher
- Ongaku
- Ongaku Shoujo
- Ongaku Shoujo (TV)
- Oni: Thunder God's Tale
- OniAi
- OniAi Specials
- Onigamiden
- Onigiri
- Onigiri ni Naritai Cogimyun
- Onihei
- Onihei: Sono Otoko, Heizou Hasegawa
- Onii-chan Dakedo Ai Sae Areba Kankeinai yo ne! Specials
- Oniichan no Koto nanka Zenzen Suki ja Nai n da kara ne!!
- Oniichan wa Oshimai!
- Oniichan wa Oshimai! (Uncensored)
- Oniisama e...
- Onikirimaru
- Onimusha
- Onipan!
- Onkyou Seimeitai Noiseman
- Only I Can Command All the Sects in the World
- Only I Can Use Summoning
- Only Yesterday
- Onmyoji Rani
- Onmyou Hyakki Monogatari
- Onmyou Taisenki
- Onmyouji
- Onna no Sono no Hoshi
- Onna Senshi Efe & Jira: Gude no Monshou
- Onsen Yousei Hakone-chan
- Ontama!
- Onyankopon
- Onyx Equinox
- Ooi! Tonbo
- Ooi! Tonbo 2nd Season
- Ookami Kakushi
- Ookami Kodomo no Ame to Yuki
- Ookami Shoujo to Kuro Ouji
- Ookami Shoujo to Kuro Ouji OVA
- Ookami Shounen Ken
- Ookami to Koushinryou (Shinsaku Anime)
- Ookami to Koushinryou II: Ookami to Kohakuiro no Yuuutsu
- Ookami to Koushinryou: Merchant Meets the Wise Wolf
- Ookami-san to Shichinin no Nakama-tachi
- Ookamikakushi
- Ookiku Furikabutte
- Ookiku Furikabutte Season 2
- Oomuro-ke: Dear Sisters
- Oooku
- Ooya-san wa Shishunki!
- Ooyukiumi no Kaina
- Ooyukiumi no Kaina: Hoshi no Kenja
- Opening Awakening Favorability System
- Opus.COLORs
- Orange
- Orange: Mirai
- Orbital Era
- Ore dake Haireru Kakushi Dungeon
- Ore dake Level Up na Ken
- Ore dake Level Up na Ken (Korean Dub)
- Ore ga Ojousama Gakkou ni "Shomin Sample" Toshite Gets♥Sareta Ken
- Ore ga Suki nano wa Imouto dakedo Imouto ja Nai
- Ore Monogatari!!
- Ore Monogatari!!
- Ore no Imouto ga Konnani Kawaii Wake ga Nai Specials
- Ore no Imouto ga Konnani Kawaii Wake ga Nai.: SD Chara ni Yoru Short Movie
- Ore no Nounai Sentakushi ga, Gakuen Love Comedy wo Zenryoku de Jama Shiteiru OVA
- Ore wa Subete wo "Parry" suru: Gyaku Kanchigai no Sekai Saikyou wa Boukensha ni Naritai
- Ore wa Teppei
- Ore wo Suki nano wa Omae dake ka yo
- Ore wo Suki nano wa Omae dake ka yo: Oretachi no Game Set
- Ore-sama Kingdom
- Ore-tachi ni Tsubasa wa Nai
- Ore, Tsushima
- Ore, Tsushima (ONA)
- Ore, Twintail ni Narimasu.
- Ore, Twintails ni Narimasu.
- Oreca Battle
- Oreimo
- OreImo 2
- Orenchi no Furo Jijou
- OreShura
- Oretachi ni Tsubasa wa Nai: Hadairo Ritsu Kyuuwari Zou!?
- Oretachi ni Tsubasa wa Nai: Under the Innocent Sky.
- Orient
- Orient: Awajishima Gekitou-hen
- Origin: Spirits of the Past
- Oroka na Tenshi wa Akuma to Odoru
- Oruchuban Ebichu
- Osake wa Fuufu ni Natte kara
- Osamu Tezuka`s Buddha Movie 1
- Osananajimi ga Zettai ni Makenai Love Comedy
- Oseam
- Oshare Kozou wa Hanamaru
- Oshi ga Budoukan Ittekuretara Shinu
- Oshiete Mahou no Pendulum: Rilu Rilu Fairilu
- Oshiete! Galko-chan
- Oshiete! Galko-chan OVA
- Oshiri Kajiri Mushi
- Osomatsu-kun
- Osomatsu-kun (1988)
- Osomatsu-san
- Osomatsu-san 2
- Osomatsu-san 2nd Season
- Osomatsu-san 3rd Season
- Osomatsu-san Movie
- Osomatsu-san Movie: Gekijou Koukai Kinen - Original Tanpen Gekijou
- Osomatsu-san Special
- Osomatsu-san Year-End Special
- Osomatsu-san: Hipipo-Zoku to Kagayaku Kajitsu
- Osomatsu-san: Ouma de Kobanashi
- Osomatsu-san: Tamashii no Takoyaki Party to Densetsu no Otomarikai
- Osu!! Karate-bu
- Otaku no Video
- OTMGirls no Yokiyoki Channel
- Otogi Juushi Akazukin
- Otogizoushi
- Otoko Ippiki Gaki Daishou
- Otokogi
- Otome Game no Hametsu Flag shika Nai Akuyaku Reijou ni Tensei shiteshimatta...
- Otome Game no Hametsu Flag shika Nai Akuyaku Reijou ni Tensei shiteshimatta... OVA
- Otome Game no Hametsu Flag shika Nai Akuyaku Reijou ni Tensei shiteshimatta... Voice Drama
- Otome Game no Hametsu Flag shika Nai Akuyaku Reijou ni Tensei shiteshimatta... X
- Otome Game Sekai wa Mob ni Kibishii Sekai desu
- Otome wa Boku ni Koishiteru
- Otome wa Boku ni Koishiteru: Trinkle Stars The Animation
- Otome Youkai Zakuro
