alphabetical list:
| Dawson O'BRIEN |  | Chol-Su O |  | Sang-Sik O | |
| Satoshi OBARA |  | Tadashi OBARA | | Yuuga OBARA | |
| Sora OBATA | | Dmitrij OBATUROV |  | Christian OBERBICHLER |  |
| Hans-Peter OBERHUBER |  | Daniil OBUKHOV |  | Dmitrij OBUSJNOJ | |
| Kazunori OCHI | | Sadayoshi OCHIAI | | Alexander OCHOWICZ |  |
| Takuro ODA | | Tomoki ODA | | Aleksandr ODEGOV |  |
| Gabriel ODOR |  | Jeroen OEBEN |  | Harald OEHME | |
| Berend OENEMA | | Johan OERLEMANS | | Hans OFFRINGA | |
| Gaweł OFICJALSKI |  | Aoi OGASAWARA | | Hirobumi OGASAWARA | |
| Yasuki OGASAWARA | | Yuuta OGASAWARA | | Yuuya OGATA | |
| Arata OGAWA | | Shouya OGAWA | | Takuro OGAWA | |
| Teruyuki OGAWA | | Toshiyuki OGAWA | | Jevgenij OGIBALOV | |
| Konstantin OGIBALOV | | Suguru OGIHARA | | Gavin OGILVIE | |
| Tatsuya OGINO | | Fumihiko OGIWARA | | Noriyuki OGIWARA | |
| Dmitrij OGLOBLIN | | Yuusuke OGUCHI | | Ivan OGURTSOV | |
| Jarosław OGÓREK | | Han-Seok OH |  | Hong-Jin OH | |
| Hyeon-Min OH | | Hyeon-Woo OH | | Je-Ho OH | |
| Jeong-Seok OH | | Joon-Oh OH | | Sang-Hoon OH | |
| Seung-Kwan OH | | Yong-Seok OH | | Yoon-Seong OH | |
| Seung-Min OHN | | Gabriel OHNMACHT |  | Kristian OHR |  |
| Torstein OHR | | Kazuya OIKAWA | | Shinobu OIKAWA | |
| Sho OIKAWA | | Yuutaro OIKAWA | | Yuuya OIKAWA | |
| Tsuki OJIMA | | Daiki OKABE | | Yuuki OKABE | |
| Itsuki OKADA | | Kakeru OKADA | | Ryo OKADA | |
| Hiroshi OKAHISA | | Gen OKAMOTO | | Taishin OKAZAKI | |
| Aleksandr OKHOTIN | | David OKONIEWSKI | | Haruki OKONOGI | |
| Kazuhiro OKUAKI | | Chikao OKUHARA | | Tsunaki OKUHARA | |
| Kazuki OKUMURA | | Tatsuya OKUMURA | | Yuuki OKUMURA | |
| Tsimafei OKUNEU |  | Sergej OKUNEV | | Igor OKUNJOV | |
| Yui OKUNO | | Daiki OKUYAMA | | John Arthur OLAFSEN | |
| Martin Emil OLAUSSEN | | Ruben OLDENBURGER | | Peter OLDENHOF | |
| Remco OLDE HEUVEL | | Wouter OLDE HEUVEL | | Aleksej OLEJNIK | |
| Andrej OLEJNIKOV | | Vladislav OLENIN | | Mikhail OLENJOV | |
| Jegor OLESKO | | Ryan OLIJNYK | | Isaiah OLIVER | |
| Niels OLIVIER | | Samuli OLLANKETO |  | Jakob OLLICK | |
| Johnny OLOF | | Mattias OLOFSSON |  | Rune OLSEN-FARSTAD | |
| Martin Stoltz OLSEN | | Willy OLSEN | | Craig OLSON | |
| Darren OLSON | | Kirk OLSON | | Paul OLSON | |
| Christian OLSSON | | Joel OLSÉN | | Tom OLTHOF | |
| Joery OLTHUIS | | Björn OLTMER | | Thorsten OLTMER | |
| Alexander OLTROP | | Zjaslan OLZJABAJEV | | Zei-Son OM | |
| Jegor OMELTSJENKO | | Hitoshi ONDA | | Kouichi ONO | |
| Ryousuke ONO | | Shouta ONO | | Suguru ONO | |
| Yasuyuki ONO | | Masaaki ONODERA | | Shunichi ONODERA | |
| Subaru ONODERA | | Kenjiro ONODZUKA | | Koujiro ONODZUKA | |
| Keigo ONOZATO | | Kouki OOBA | | Masaki OOBA | |
| Kou OOBAYASHI | | Masahito OOBAYASHI | | Takahiro OOE | |
| Takehiro OOE | | Tomoki OOFUJI | | Ryo OOGAKI | |
| Hiroyuki OOHASHI | | Tomomi OOHASHI | | Kouji OOHIRA | |
| Akira OOI | | Takenori OOI | | Mark OOIJEVAAR | |
| Akihiko OOISHI | | Takuya OOISHI | | Ryuutaro OOIZUMI | |
| Satoshi OOKE | | Kazumitsu OOKUBO | | Yuuta OOKUBO | |
| Yuutaro OOKUMA | | Naokazu OOKURA | | Johannes OOMEN | |
| Ryuuichi OOMICHI | | Ryuunosuke OOMICHI | | Yasuhiro OOMICHI | |
| Hiroshi OOMIYA | | Eiji OOMORI | | Fuyuki OOMORI | |
| Masahiko OOMURA | | Ichiro OONISHI | | Tomonori OONISHI | |
| Yuusuke OONISHI | | Yuusuke97 OONISHI | | Haruki OONO | |
| Natsu OONO | | Eiji OONUKI | | Bram OORT | |
| Bungo OOSAKA | | Kouki OOSAKI | | Takuya OOSAKI | |
| Takashi OOSATO | | Kenta OOSAWA | | Wataru OOSAWA | |
| Souki OOSHIMA | | Takahiro OOSHIMA | | Tatsuki OOSHIMA | |
| Kouki OOSHUU | | Renki OOSHUU | | Jorrit OOSTEN | |
| Roderick OOSTEN | | Gert-Jan OOSTERBOS | | Dirk OOSTERINK | |
| Fred OOSTERLAAN | | Akio OOTA | | Ayato OOTA | |
| Masahito OOTA | | Masakiyo OOTA | | Akito OOTAKE | |
| Takuzo OOTAKE | | Hitoshi OOTANAKA | | Yushi OOTANAKA | |
| Stefan OOTES | | Daisuke OOTOUGE | | Seitaro OOTOUGE | |
| Takanori OOTSU | | Tatsuki OOTSUKA | | Amon OOTSUKI | |
| Riku OOTSUKI | | Takahiro OOTSUKI | | Yuuta OOTSUKI | |
| Takuma OOUCHI | | Tomonori OOUCHI | | Kouji OOWADA | |
| Makoto OOWADA | | Tsukasa OOWADA | | Kantaro OOYAMA | |
| Kousuke OOYANAGI | | Denis OPALEV | | Artur OPALIŃSKI | |
| Ivan OPARIN | | Ion OPINCARIU |  | Alexandru Vlad OPREA | |
| Sebastiaan ORANJE | | Eemil-Oskar ORAS | | Gavin ORD | |
| Jeroen OREMUS | | Roman ORESJIN | | Aleksandr ORESJKIN | |
| Bat-Erdene ORGIL |  | Jacques ORIE | | Kenshin ORIKASA | |
| Norio ORIKAWA | | Yuushin ORITA | | John ORLIKOW | |
| Kelly ORLOFF | | Boris ORLOV | | Jurij ORLOV | |
| Mikhail ORLOV | | Oleg ORLOV | | Sergej ORLOV | |
| Vladimir ORLOV | | Vladislav ORLOV | | Eric ORLOWSKY | |
| João Francisco ORNELAS DE JESUS |  | Khyl ORSER | | Liam ORTEGA | |
| Kaito OSADA | | Manabu OSADA | | Tsubasa OSADA | |
| Nikita OSADTSJIJ | | Takafumi OSAME | | Shintaro OSANAI | |
| Seijuuro OSANO | | Toshiyuki OSANO | | Rasjid OSIN | |
| Wierd OSINGA | | Dmitrij OSIPENKO | | Aart OSKAM | |
| Hidetoshi OSODA | | Oleg OSOKIN | | Michał OSTASZEWSKI | |
| Aleksandr OSTROVSKIJ | | Vjatsjeslav OSTROVSKIJ | | Paweł OSTROWSKI | |
| Shunya OTANI | | Gabriel OTHENIN-GIRARD | | Steffen Floor OTNÆS | |
| Yoshimi OTSUKI | | Niels OTT | | Tom-Benedikt OTT | |
| Bas OTTEN | | Ivar OTTENBROS | | Kai-Arne OTTENHOFF | |
| Arjan OTTENS | | Coen OTTERSPEER | | Hein OTTERSPEER | |
| Muncef OUARDI | | Job OUDE VRIELINK | | Tim OUDE WOLCHERINK | |
| Simon OUDSHOORN | | Ton OUDSHOORN | | Vincent OUDSHOORN | |
| John OUDT | | Alphonse OUIMETTE | | Mitch OUT | |
| Steven OUTEN |  | Aleksandr OVDIN | | Ad OVERDEVEST | |
| Arjan OVERDEVEST | | Thomas OVEREND | | Jeremy OVERHEUL | |
| Rickardo OVERHEUL | | Kevin OVERLAND | | Jelle OVERMARS | |
| Pieter OVERMARS | | Jay OVERVLIET | | Niels OVERVOORDE | |
| Leif Marius OVLI | | Aleksandr OVRAZJKO | | Sergej OVSJANNIKOV | |
| Aleksandr OVTSJARENKO | | Aleksandr OVTSJINNIKOV | | Maksim OVTSJINNIKOV | |
| Mateusz OWCZAREK | | Christian OWESEN | | Tom Erik OXHOLM | |
| Kouki OYAMA | | Mikio OYAMA | | Shousuke OYAMA | |
| Haruki OZAWA | | Nao OZAWA | | Ryuuichi OZAWA | |
| Igor OZEROV | |
