| Abdelkrim Ben Osman (Alg) | Adam Olbrich (Gbr) | Adel Ourahmoune (Alg) | Adem Ozmeral (Tur) |
| Agustin Boje-Ordonez (Esp) | Ahmed Ouadane (Alg) | Albano Olivetti (Fra) | Alejandro Olivera (Uru) |
| Aleksiy Ostapets (Ukr) | Alex Osterrieth (Gbr) | Alexander Olsson (Swe) | Alexandru Oichea (Rou) |
| Alvaro Izquierdo-Ordovas (Esp) | Alvaro Raposo De Oliveira (Per) | Amine El Ouazzani (Mar) | Andre Oliveira (Por) |
| Andrei Olhovskiy (Rus) | Andrei-Gratian Onciu (Rou) | Andres Osorio (Ecu) | Angelo Orsini (Ita) |
| Antoni Orlinski (Pol) | Antonio Canadillas-Ortiz (Esp) | Arata Onozawa (Jpn) | Atsuo Ogawa (Jpn) |
| Badr Ouabdelmoumen (Mar) | Benjamin Osterbrink (Ger) | Bolaji Olawepo (Ngr) | Boris Obama (Fra) |
| Bostjan Osabnik (Slo) | Bowen Ouyang (Hkg) | Brian Orradre (Arg) | Bruno Oresar (Cro) |
| Bunya Ozaki (Jpn) | Carlos Oliveira (Bra) | Constantin Obretin (Rou) | Dae-Soung Oh (Kor) |
| Daniel Montes De Oca (Uru) | Daniel Omana (Ven) | Daniel Oppe (Gbr) | Daniel Orsanic (Arg) |
| Daniel Osborne (Aus) | Daniel Uson-Olaso (Esp) | David Olave (Col) | David Orces (Ecu) |
| Dawid Olejniczak (Pol) | Dennis Ochieng (Ken) | Diego Oliveira (Bra) | Diego Ollague (Ecu) |
| Diego Orellana (Chi) | Djanibek Orazoliev (Uzb) | Djerald Oganezov (Geo) | Donny Opici (Usa) |
| Eduardo Oaxaca (Mex) | Edward Louies Oueilhe (Usa) | Emmanuel Olivier (Mex) | Enrique Olivares (Ven) |
| Erhan Oral (Tur) | Esben Hess-Olesen (Den) | Esteban Ordonez (Ecu) | Ezequiel Velez-Ortiz (Esp) |
| Fabrizio Ornago (Ita) | Federico Ottolini (Ita) | Felipe Gonzalez-Orellana (Chi) | Felipe Ortiz (Chi) |
| Fernando Agustin Ordonez (Arg) | Francisco Carrillo-Onieva (Esp) | Francisco Olivares (Chi) | Gabriel Olocco (Arg) |
| Gabriel Otu (Ngr) | Giacomo Oradini (Ita) | Godwin Omuta (Ngr) | Goran Oresic (Cro) |
| Graydon Oliver (Usa) | Gregor Opferman (Ger) | Gregory Ouellette (Usa) | Guilherme Ochiai (Bra) |
| Guillermo Alcorta-Olarra (Esp) | Guillermo Olaso (Esp) | Hernando Ortiz (Col) | Hiromasa Oku (Jpn) |
| Hironobu Ohguri (Jpn) | Hiroshi Ohata (Jpn) | Horatiu-Razvan Oltean (Rou) | Hosam Osman (Sud) |
| Ignacio Ortiz (Col) | Igor Ogrinc (Slo) | Igor Ogrizek (Cro) | Igor Okamoto (Bra) |
| Ilia Ogarkov (Rus) | Ilija Ognenovski (Mkd) | Ilja Orre (Fin) | Inigo Ojer (Ven) |
| Jacob Olsen (Nzl) | Jaime Oncins (Bra) | Jakub Ondrias (Svk) | Janne Ojala (Fin) |
| Javier Ottaviani (Arg) | Jesus Patino-Otero (Mex) | Jesus-Esteban Marquet-Ojeda (Esp) | Joao Oliveira (Bra) |
| Johan Olsson (Swe) | Johan Ortegren (Swe) | Johannes Robert Van Overbeek (Usa) | John Otu (Ngr) |
| John Oyet (Uga) | Jonathan Otero (Col) | Jose Ordaz (Ven) | Joshua Olivas (Usa) |
| Joshua Osswald (Usa) | Josselin Ouanna (Fra) | Juan Pablo Ortiz (Arg) | Juan S. Orozco (Col) |
| Juan-Carlos Osorio (Ecu) | Juan-Pablo Ospina (Col) | Julian Onken (Ger) | Julien Obry (Fra) |
| Julien Onclin (Bel) | Julio-Cesar Garza-Oranday (Mex) | Junior A. Ore (Usa) | Justin Obront (Bah) |
| Juuso Ojanen (Fin) | Kacper Owsian (Pol) | Kai Ohuchi (Jpn) | Kazuhito Oshima (Jpn) |
| Kazuya Ono (Jpn) | Ken Onoda (Jpn) | Kepler Orellana (Ven) | Khalid Outaleb (Mar) |
| Kota Okazaki (Jpn) | Lamine Ouahab (Alg) | Leon Ojalvo (Usa) | Leonardo Olguin (Arg) |
| Luca Ottavi (Ita) | Lucas Oliveira (Bra) | Luka Ocvirk (Slo) | Lukas Ollert (Ger) |
| Maciej Ochocinski (Pol) | Magin Ortiga (Col) | Magnus Ohrvall (Swe) | Malino Oda (Usa) |
| Marco Ortwein (Ger) | Marco Osorio (Mex) | Marco Ricardo Osorio (Hon) | Marcos Esparcia Omedas (Esp) |
| Marcos Facundo-Oliveira (Bra) | Marcos Ondruska (Rsa) | Marcus Harder-Otto (Ger) | Mark Oljaca (Usa) |
| Mark Ozer (Usa) | Marko Ostoja (Cro) | Marlon Oliveira (Bra) | Martin Orsula (Svk) |
| Marton Ott (Hun) | Massimo Ocera (Ita) | Matias Oddone (Arg) | Matic Omerzel (Slo) |
| Matt Ogle (Usa) | Maurice van Oosten (Ned) | Maxence Olivier (Fra) | Maximilian Ortiz (Usa) |
| Menford Owusu (Gha) | Menno Oosting (Ned) | Michael Ouvarov (Gbr) | Michal Olejniczak (Pol) |
| Michihisa Onoda (Jpn) | Miroslav Ocadlik (Cze) | Mitja Ogrizek (Slo) | Mohamed-Redha Ouahab (Alg) |
| Mohammed-Faizal Bin Othman (Mas) | Nathan Overholser (Usa) | Nduka Odizor (Ngr) | Nicolas Daniel Olguin (Ger) |
| Nicolas Gutierrez-De La Osa (Esp) | Noam Okun (Isr) | Ogidi Obi (Usa) | Oleg Ogorodov (Uzb) |
| Oleg Ouchakov (Rus) | Oleksiy Odazhyu (Ukr) | Oliver Oreskowitz (Ger) | Oscar Ortiz (Mex) |
| Oscar Otte (Ger) | Othman Zerouali-Ouariti (Can) | Pablo Romero-Otero (Esp) | Patricio Olvera (Ecu) |
| Patrick Ochan (Uga) | Patrick Ofner (Aut) | Patrick Olobo (Uga) | Patrick Ostheimer (Ger) |
| Patrick Osuna (Usa) | Pedro Nieto-Orellana (Esp) | Petr Olsak (Cze) | Philip Orno (Den) |
| Philipp Oswald (Aut) | Philippe Oudshoorn (Ned) | Piotr Olechowski (Pol) | Raphael Oezelli (Ger) |
| Renzo Olivo (Arg) | Revaz Osadze (Geo) | Ricardo Oliveira (Bra) | Ricardo Omana (Ven) |
| Ricards Opmanis (Lat) | Ricki Osterthun (Ger) | Roberto Ortega-Olmedo (Esp) | Roberto Ovallez (Mex) |
| Robin Olin (Swe) | Rodrigo Orozco (Arg) | Roel Oostdam (Ned) | Roger Ordeig (Esp) |
| Roman Ogarkov (Rus) | Ryo Oki (Jpn) | Santiago Ordonez (Ecu) | Scott Oudsema (Usa) |
| Sebastian Gonzalez-Obregoso (Per) | Seong-Gook Oh (Kor) | Seong-Yook Oh (Kor) | Sergio Olivares (Ven) |
| Seung-Hoon Oh (Kor) | Shinnosuke Otsuka (Jpn) | Shiv Oberoi (Can) | Sobir Ochilov (Uzb) |
| Soren Hess-Olesen (Den) | Souleymane Ouedraogo (Bur) | Taiwo Owolabi (Ngr) | Takao Ohno (Jpn) |
| Talal Ouahabi (Mar) | Tan-Luc On (Vie) | Thomas Oechel (Usa) | Thomas Oger (Mon) |
| Tiago Olimpio (Por) | Tobias Obenaus (Aut) | Tomasz Olfans (Pol) | Tuomo Ojala (Fin) |
| Ugljesa Ostojic (Bih) | Uriel Oquendo (Col) | V?tor Oliveira (Bra) | Victor Ouvrard (Fra) |
| Vincent Owens (Usa) | Vinko Ojdanic (Cro) | Vladimir Obradovic (Srb) | Wade Orr (Usa) |
| Walter Orth (Ger) | Wayne Odesnik (Usa) | Wojciech Owsiak (Pol) | Yaseen Obaray (Rsa) |
| Yohei Okuno (Jpn) | Yoichiro Oka (Jpn) | Yuji Oyama (Jpn) |
