alphabetical list:
| Dawson O'BRIEN |  | Chol-Su O |  | Sang-Sik O | |
| Satoshi OBARA |  | Tadashi OBARA | | Yuuga OBARA | |
| 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 |  |
| Hirobumi OGASAWARA | | Yasuki OGASAWARA | | Yuuta OGASAWARA | |
| Yuuya OGATA | | Arata OGAWA | | Shouya OGAWA | |
| Takuro OGAWA | | Teruyuki OGAWA | | Toshiyuki OGAWA | |
| Jevgenij OGIBALOV | | Konstantin OGIBALOV | | Suguru OGIHARA | |
| 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 | |
| Gabriel OHNMACHT |  | Kristian OHR |  | Torstein OHR | |
| Kazuya OIKAWA | | Shinobu OIKAWA | | Sho 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 | |
| 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 | | 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 | | Zei-Son OM | | Jegor OMELTSJENKO | |
| Hitoshi ONDA | | Kouichi ONO | | Ryousuke ONO | |
| Shouta ONO | | Suguru ONO | | Yasuyuki ONO | |
| Masaaki ONODERA | | Shunichi ONODERA | | Kenjiro ONODZUKA | |
| Koujiro ONODZUKA | | Keigo ONOZATO | | Kouki OOBA | |
| Masaki OOBA | | Kou OOBAYASHI | | Masahito OOBAYASHI | |
| Takahiro 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 | | 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 | | Kousuke OOYANAGI | | Denis OPALEV | |
| Artur OPALIŃSKI | | Ivan OPARIN | | Ion OPINCARIU |  |
| Alexandru Vlad OPREA | | Sebastiaan ORANJE | | Eemil-Oskar ORAS | |
| 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 | | Eric ORLOWSKY | | Khyl ORSER | |
| Liam ORTEGA | | Kaito OSADA | | Manabu OSADA | |
| Tsubasa OSADA | | Nikita OSADTSJIJ | | Takafumi OSAME | |
| Shintaro OSANAI | | 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 | | 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 | |
| Ryuuichi OZAWA | | Igor OZEROV | |
