Anime Series Beginning with O
- Osama Ranking
- Osananajimi ga zettai ni makenai love-come
- Osen
- Oshi ga Budokan Ittekuretara Shinu
- Oshigoto Danshi
- Oshiri Tantei
- Osomatsu-san
- Ossan's Love
- Otaku Elf
- Otaku ni Koi wa Muzukashii
- Otenki Sentai How Weather
- Otherside PIcnic
- Otobun
- Otoca Doll
- Otogi Jushi Akazukin
- Otoko wa Tsuraiyo
- Otome continue
- Otome wa Boku ni Koishiteru
- Otome Yokai Zakuro
- Otona Anime
- Ouran Koko Host Club
- Outbreak Company
- Over Drive
- Overlord
- Overman King-Gainer
- Overtake!
- Oyuki Umi no Kina
- OZMAFIA!!
- Ozuma
- Please Tell Me! Galko-chan
- Scenes from Awajima (Awajishima Hyakkei)
- Seraph of the End
- Shomin Sample
- The Other World's Books Depend on the Bean Counter
- The Royal Tutor (Oshitsu Kyoshi Haine)
- Uncle from Another World