Characters Which Start with [O]
- Obeiron (Sugou Nobuyuki)
- Obelisk the Tormentor
- Oberon (Fate Series) (オベロン)
- Oboro
- Oboro (Kan Colle)
- Oda Nobuhime
- Oda Nobukatsu (Fate Series)
- Oda Nobunaga (Drifters)
- Oda Nobunaga (Fate Series)
- Oda Raika
- Oga Akita
- Oga Saki
- Ogami Ichiro
- Ogami Tamaki
- Ogasawara Haruka
- Ogasawara Rinko
- Ogasawara Sachiko
- Ogata Kanna (尾刃カンナ)
- Ogata Rina
- Ogata Rizu
- Ogawa shinji
- Ogin (GIRLS-und-PANZER)
- Ogiso Setsuna
- Ogiue Chika
- Oguri Cap (Uma Musume)
- Ohara Mari
- Ohara Rinne
- Ohr (Blue Archive) (オウル)
- Oichi
- Oikawa Shizuku
- Oikawa Toru
- Oikura Sodachi
- Oji Mochizo
- Oka Asahi (桜花あさひ)
- Oka Mikino
- Okabe Rintarou
- Okada Izou (Fate Series)
- Okamoto Miyuu
- Okamura Nao
- Okazaki Kumi
- Okazaki Tomoya
- Okazaki Yasuha
- Okazaki Yumemi
- Oki Aoi (扇喜アオイ)
- Okinami (Kan Colle)
- Okita Jyuuzou
- Okita Kyouko
- Okita Sawa
- Okita Sougo
- Okita Souji (Alter)
- Okita Souji (Fate Series)
- Okitsu Yuka
- Okouchi Akira
- Okto (Princess Connect Re:Dive)
- Okudera Miki
- Okumura Haru
- Okura Miyako
- Okusawa Misaki
- Okusora Ayane (奥空アヤネ)
- Okuzaki Akira
- Oldrin Zevon
- Olga (Magia Record) (オルガ)
- Olga Discordia
- Olga Janetine
- Olga Marie Animusphere
- Olivia (Asobi Asobase)
- Olivia (Lychee)
- Olivier Lenheim
- Olivier Mira Armstrong
- Oma Kokichi
- Omagari Hare (小鈎ハレ)
- Omaru Polka
- Omega Ray (おめがレイ)
- Omega Rio (おめがリオ)
- Omiya Shinobu
- Omori Yuko (Cure Honey)
- Onaga Akino
- ONE (VOCALOID)
- Onikata Kayoko (鬼方カヨコ)
- Onitsuka Natsumi (鬼塚夏美)
- Onitsuka Tomari (鬼塚冬毬)
- Ono Kanako
- Onoda Sakamichi
- Onodera Haru
- Onodera Kosaki
- Onozuka Komachi
- Onsoku no Sonic
- Onuma Kurumi
- Oodenta Mitsuyo (Touken Ranbu)
- Oogaki Chiaki
- Oogami Marina
- Oohara Michiru
- Oohoshi Awai
- Ooi (Kan Colle)
- Ooishi Izumi
- Ookami Mio (大神ミオ)
- Ooki Futaba
- Ookurikara
- Oomichi Asahi
- Oomichi Miyabi
- Oono Akira
- Oono Aya
- Oono Makoto
- Oono Tsukuyo (大野ツクヨ)
- Oosaka Naru
- Ooshio (Azur Lane)
- Ooshio (Kan Colle)
- Ootori Chacha
- Ootori Chihaya
- Ootori Miou
- Ooyodo (Kan Colle)
- Oozora Akari
- Oozora Haruka
- Oozora Subaru
- Ophelia Phamrsolone
- Orange Pekoe
- Oreki Houtarou
- Orga Itsuka
- Oriana Thomson
- Oribe Yasuna
- Oriental Small-clawed Otter (Kemono Friends)
- Orifushi Mafuyu
- Origami Hina
- Orikasa Ayumu
- Orimura Chifuyu
- Orimura Ichika
- Orion (Fate Series)
- Orsola Aquinas
- Ortfiné Fredericka von Eylstadt
- Ortlinde (Fate Series)
- Oryou (GIRLS-und-PANZER) (Nogami Takeko)
- Oryou-san (Fate Series)
- Osakabehime (Fate Series)
- Osaki Amana
- Osaki Tenka
- Osawa Rurino (大沢瑠璃乃)
- Oshida (GIRLS-und-PANZER)
- Oshimizu Nako
- Oshino Meme
- Oshino Ougi
- Oshutoru
- Otani Momoko
- Otogi (Blue Archive) (オトギ)
- Otogibara Era
- Otoha Umeki
- Otohana Sumire
- Otohime Mutsumi
- Otokura Yuuki
- Otomachi Una
- Otomune Kozue (乙宗 梢)
- Otonashi Kiruko
- Otonashi Kyoko
- Otonashi Yuzuru
- Otone Nicole
- Otosaka Ayumi
- Otose Kotama (音瀬コタマ)
- Otoshiro Noel
- Otoshiro Seira
- Otoya Ittoki
- Ou Genki
- Ouka Miko
- Ouro Kronii (オーロ・クロニー)
- Ouroboros (Girls' Frontline)
- Ousaka Shizuku
- Ouzen (Made in Abyss)
- Owari (Azur Lane) (尾張)
- Owari Akane
- Owari Hajime
- Oyama Mahiro (緒山まひろ)
- Oyama Mihari (緒山みはり)
- Oyashio (Kan Colle)
- Ozaki Reiko
- Ozymandias (Fate Series)