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 | | Ryuusei 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 | |
| Hylke OOSTERHOF | | 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 | |
| Issei OZAWA | | Nao OZAWA | | Ryuuichi OZAWA | |
| Igor OZEROV | |
