| O, Yeong Gon | |
| O, Yanhong | |
| O Antikythira, Noah | Anime: It's My Life |
| O Antikythira, Elizabeth (Elise) | Anime: It's My Life |
| O'Brian, Naomi | Anime: Kanojo ga Koushaku-tei ni Itta Riyuu |
| O'Brian, Abigail | |
| O'Brien, Zeke (Black Knight) | |
| O'Brien, Marty | Anime: Golgo 13 (TV) |
| O'Brien, Nina | Anime: Macross Δ, Macross Δ Movie: Gekijou no Walküre |
| O'Brien, Patricia (Pat) | Anime: Kindaichi Shounen no Jikenbo |
| O'Brien, Kurisu Kyoji | Anime: Psycho-Pass 3 |
| O'Connell, Flop (Flora) | |
| O'Connell, Medium | |
| O'Drielle, Makia | |
| O'Hara, Joyce | Anime: Tousouchuu: Great Mission |
| O'Hara-St. Jones, Scarlett | Anime: Steamboy |
| O'Malley, Grace | Anime: Kaizoku Oujo |
| O'naill, Biz | Anime: Cop Craft |
| O'Neil, Amelia | |
| O'Brian, Patricia (Patty) | Anime: Candy Candy, Candy Candy: Candy no Natsu Yasumi |
| O'Brian, Mariko | Anime: Junk Story: Tetsukuzu Monogatari |
| O'Brian, Alex | Anime: Baby Steps 2nd Season |
| O'Brian, Marcia | Anime: Baby Steps 2nd Season |
| O'Brien, Emily | Anime: Lupin III: Tenshi no Tactics - Yume no Kakera wa Koroshi no Kaori |
| O'Brien, Austin (Axel Brodie) | Anime: Yu☆Gi☆Oh! Duel Monsters GX |
| O'Brien, Thomas | Anime: Ashita no Nadja |
| O'Brien, Steve | Anime: Moonlight Mile 1st Season: Lift Off, Moonlight Mile 2nd Season: Touch Down |
| O'Brien, Zed | Anime: Kekkai Sensen, Kekkai Sensen: Ousama no Restaurant no Ousama, Kekkai Sensen & Beyond, Kekkai Sensen & Beyond: Zapp Renfro Ingaouhouchuu!!/Baccardio no Shizuku |
| O'Connell, Daniel | Anime: Master Keaton, Master Keaton OVA |
| O'Conner, Doris | Anime: Marmalade Boy |
| O'Conner, Sam | Anime: Eightman After |
| O'Conner, Jack | Anime: Eightman After |
| O'Connor, Grace | Anime: Macross F, , Macross F Movie 1: Itsuwari no Utahime, Macross F Movie 2: Sayonara no Tsubasa |
| O'Connor, Arthur | Anime: Tom Sawyer no Bouken |
| O'Hara, Paige | |
| O'Hara, Emily | Anime: City Hunter: Hyakuman Dollar no Inbou |
| O'Hara, Tachi | Anime: Kidou Senshi Gundam, Kidou Senshi Gundam: The Origin, Kidou Senshi Gundam: The Origin - Zenya Akai Suisei |
| O'Hara, Francesca | Anime: Kidou Senshi Victory Gundam |
| O'Hare, Katharine (Crasher) | |
| O'Huey, Volcott (The White Supernova Wolf, Valdmir Volcott) | Anime: Galaxy Angel, Galaxy Angel Z, Galaxy Angel 3, Galaxy Angel 3 Specials, Galaxy Angel 4, Galaxy Angel Music Collection: Shouen to Shien no Cassoulet, Galaxy Angel Specials |
| O'Keefe, Margaret (Special Service Agent) | Anime: Buddy Complex, Buddy Complex: Kanketsu-hen - Ano Sora ni Kaeru Mirai de |
| O'Malley, Grace (Pirate Queen) | Anime: Kyoukaisenjou no Horizon II |
| O'Neil, April | Anime: Mutant Turtles: Choujin Densetsu-hen |
| O'Neil, Vanessa | Anime: Eat-Man '98 |
| O'Neil, Tetto | Anime: Eat-Man '98 |
| O'Neill, Sam (Knight) | Anime: Gosick |
| O'Neill, Ginger | |
| O'Neill, Amanda | Anime: Little Witch Academia: Mahoujikake no Parade, Little Witch Academia (TV) |
| O'Reilly | Anime: Rocket Girls |
| O'Rourke, Kane | |