Otome Series Beginning with O
- [Oshi no ko]
- My Next Life as a Villainess: All Routes Lead to Doom!
- Obey Me!
- Occultic;Nine
- Octave
- OCTOPATH TRAVELER
- Oda Nobuna no Yabou
- Oda Shinamon Nobunaga
- Odd Taxi
- Oedo Rocket
- Oh-oku ( Danjo Gyakuten)
- Oishi Propose
- Oishinbo
- Ojamajo
- Ojarumaru
- Ojisama (warai) Series
- Ojisama Senka
- Okami Shojo to Kuro Oji
- Okami to Koshinryo (Wolf and Spice)
- Okane ga Nai!
- Okasan to Issho
- Okiku Furikabutte
- Okoshiyasu Chitose Chan
- Okusama ga Seito Kaicho!
- Okusama wa Maho Shojo
- Olympic
- Omae Umasodana
- Omamori Himari
- Omoi, Omoware, Furi, Furare
- Omoide no Marnie (When Marnie Was There)
- Omukaedesu.
- ONE - Kagayaku Kisetsu e
- One Piece
- One Punch Man
- Onegai My Melody
- Onegai Teacher (Please Teacher!)
- Onegai Twins
- Ongaku to Hito
- Onichan Dakedo Ai Sae Areba Kankeinaiyone
- Onigamiden
- Onigiri
- Onihei Hankacho
- Onimusha
- Onkyokaiwa
- Online Game
- Onna no Sono no Hoshi
- Onosaka, Konishi no O+K(OTASUKE)
- Ookami-san Series
- Ooya-san wa Shishunki !
- Opus.COLORs
- orange
- Ordian
- Ore monogatari!!
- Ore no Imoto ga Kon nani Kawaii wake ga nai
- Ore no Kanojo to Osananajimi ga Shuraba Sugiru
- Ore o Suki nano wa Omae dake kayo
- Orenchi no Furo Jijyo
- Oretachi Majikou Destroy
- Oretachin ni Tsubasa wa Nai
- Orient
- Osama Game
- Osama Ranking
- Osananajimi ga zettai ni makenai love-come
- Oshi ga Budokan Ittekuretara Shinu
- Oshigoto Danshi
- Oshiri Tantei
- Osomatsu-san
- Ossan's Love
- Otaku ni Koi wa Muzukashii
- Otenki Sentai How Weather
- Otobun
- Otogi Jushi Akazukin
- Otome continue
- Otome Yokai Zakuro
- Otona Anime
- Ouran Koko Host Club
- Outbreak Company
- Over Drive
- Overlord
- Overman King-Gainer
- OZMAFIA!!
- Ozuma
- Please Tell Me! Galko-chan
- Seraph of the End
- The Royal Tutor (Oshitsu Kyoshi Haine)