O（62）
- Active Players
- O
O
- 38 Infielder
- Obata, Ryuhei
- Hanshin Tigers
- 00 Outfielder
- Oda, Gouki
- Chunichi Dragons
- 3 Infielder
- Oda, Koichiro
- YOKOHAMA DeNA BAYSTARS
- 125 Infielder (*)
- Ogasawara, Sou
- YOKOHAMA DeNA BAYSTARS
- 57 Outfielder
- Ogata, Riku
- Fukuoka SoftBank Hawks
- 39 Pitcher
- Ogata, Shuto
- Fukuoka SoftBank Hawks
- 122 Pitcher (*)
- Ogawa, Ippei
- Hanshin Tigers
- 57 Infielder
- Ogawa, Ryusei
- Chiba Lotte Marines
- 29 Pitcher
- Ogawa, Yasuhiro
- Tokyo Yakult Swallows
- 51 Outfielder
- Ogoh, Yuya
- Tohoku Rakuten Golden Eagles
- 150 Infielder (*)
- Ohashi, Reo
- Fukuoka SoftBank Hawks
- 29 Pitcher
- Ohe, Ryusei
- Fukuoka SoftBank Hawks
- 123 Outfielder (*)
- Ohizumi, Shuya
- Fukuoka SoftBank Hawks
- 27 Pitcher
- Ohkawa, Jey
- Hokkaido Nippon-Ham Fighters
- 46 Pitcher
- Ohmichi, Haruki
- Tokyo Yakult Swallows
- 59 Outfielder
- Ohmori, Minoru
- Hiroshima Toyo Carp
- 44 Pitcher
- Ohnishi, Hiroki
- Tokyo Yakult Swallows
- 60 Pitcher
- Ohno, Kazuo
- Fukuoka SoftBank Hawks
- 22 Pitcher
- Ohno, Yudai
- Chunichi Dragons
- 16 Pitcher
- Ohnuki, Shinichi
- YOKOHAMA DeNA BAYSTARS
- 72 Catcher
- Ohsakae, Toshiya
- Tohoku Rakuten Golden Eagles
- 122 Infielder (*)
- Ohsato, Kosei
- ORIX Buffaloes
- 14 Pitcher
- Ohsera, Daichi
- Hiroshima Toyo Carp
- 8 Outfielder
- Ohshima, Yohei
- Chunichi Dragons
- 10 Infielder
- Ohshiro, Koji
- ORIX Buffaloes
- 24 Catcher
- Ohshiro, Takumi
- Yomiuri Giants
- 2 Catcher
- Ohta, Hikaru
- Tohoku Rakuten Golden Eagles
- 1 Infielder
- Ohta, Ryo
- ORIX Buffaloes
- 136 Pitcher (*)
- Ohtake, Fuga
- Fukuoka SoftBank Hawks
- 21 Pitcher
- Ohtake, Koutaro
- Hanshin Tigers
- 31 Pitcher
- Ohtani, Hikaru
- Chiba Lotte Marines
- 125 Catcher (*)
- Ohtomo, Sou
- Fukuoka SoftBank Hawks
- 19 Pitcher
- Ohtsu, Ryosuke
- Fukuoka SoftBank Hawks
- 129 Outfielder (*)
- Ohtsubo, Shion
- Tohoku Rakuten Golden Eagles
- 49 Infielder
- Ohtsuka, Ruan
- Hokkaido Nippon-Ham Fighters
- 67 Pitcher
- Ohuchi, Seiya
- Tohoku Rakuten Golden Eagles
- 146 Pitcher (*)
- Ohya, Ryusei
- Fukuoka SoftBank Hawks
- 164 Pitcher (*)
- Ohyama, Hokuto
- Fukuoka SoftBank Hawks
- 53 Pitcher
- Ohyama, Ryo
- Fukuoka SoftBank Hawks
- 3 Infielder
- Ohyama, Yusuke
- Hanshin Tigers
- 47 Pitcher
- Ohzeki, Tomohisa
- Fukuoka SoftBank Hawks
- 14 Pitcher
- Ojima, Kazuya
- Chiba Lotte Marines
- 25 Outfielder
- Oka, Hiromi
- Chiba Lotte Marines
- 1 Outfielder
- Okabayashi, Yuki
- Chunichi Dragons
- 140 Pitcher (*)
- Okada, Koichiro
- Fukuoka SoftBank Hawks
- 38 Outfielder
- Okada, Yuki
- Yomiuri Giants
- 64 Pitcher
- Okadome, Hidetaka
- Hanshin Tigers
- 53 Pitcher
- Okamoto, Shun
- Hiroshima Toyo Carp
- 69 Catcher
- Okamura, Ryoju
- Chiba Lotte Marines
- 34 Outfielder
- Okashiro, Kaisei
- Hanshin Tigers
- 162 Pitcher (*)
- Okaue, Jumpei
- Fukuoka SoftBank Hawks
- 18 Pitcher
- Okugawa, Yasunobu
- Tokyo Yakult Swallows
- 116 Outfielder (*)
- Okumura, Koichi
- Saitama Seibu Lions
- 40 Pitcher
- Okumura, Raito
- Chiba Lotte Marines
- 145 Pitcher (*)
- Oliver, Ronny
- Saitama Seibu Lions
- 37 Pitcher
- Ono, Fumiya
- Chiba Lotte Marines
- 60 Outfielder
- Onodera, Dan
- Hanshin Tigers
- 13 Infielder
- Osuna, Jose
- Tokyo Yakult Swallows
- 54 Pitcher
- Osuna, Roberto
- Fukuoka SoftBank Hawks
- 15 Pitcher
- Ota, Taisei
- Yomiuri Giants
- 37 Pitcher
- Oyokawa, Masaki
- Hanshin Tigers
- 173 Outfielder (*)
- Ozuna, Jose
- Fukuoka SoftBank Hawks