- Jack Catterall (Boxing)
- Jack Cullen (Boxing)
- Jackson State (American Football)
- Jackson State (Basketball)
- Jacksonville Jaguars (American Football)
- Jacksonville State (American Football)
- Jacksonville State (Basketball)
- Jade Bornea (Boxing)
- Jade Jets Women (Cricket)
- Jaffna (Cricket)
- Jaffna Kings (Cricket)
- Jagiellonia Białystok (Football)
- Jaguares (Rugby Union)
- Jahn Regensburg (Football)
- Jai Opetaia (Boxing)
- Jaime Arboleda (Boxing)
- Jaime Munguia (Boxing)
- Jake Paul (Boxing)
- Jamaica (Football)
- Jamaica (Netball)
- Jamaica (Rugby League)
- Jamaica (Cricket)
- Jamaica (Tennis)
- Jamaica Tallawahs (Cricket)
- Jamaica Women (Football)
- Jamaica Women (Lacrosse)
- Jamaica Women (Cricket)
- Jamaine Ortiz (Boxing)
- Jamel Herring (Boxing)
- James Beech (Boxing)
- James DeGale (Boxing)
- James Madison (American Football)
- James Madison (Basketball)
- James Metcalf (Boxing)
- Jammu & Kashmir (Cricket)
- Jammu & Kashmir Women (Cricket)
- Jammu Janbaz (Cricket)
- Janibek Alimkhanuly (Boxing)
- Japan (Football)
- Japan (Rugby Union)
- Japan (Tennis)
- Japan (Basketball)
- Japan (Volleyball)
- Japan (Hockey)
- Japan (Baseball)
- Japan (Cricket)
- Japan U20 (Rugby Union)
- Japan Under-19s (Cricket)
- Japan Women (Football)
- Japan Women (Cricket)
- Japan Women (Rugby Union)
- Japan Women (Basketball)
- Japan Women (Lacrosse)
- Japan Women (Hockey)
- Japan Women (Volleyball)
- Japan XV (Rugby Union)
- Jared Anderson (Boxing)
- Jaron Ennis (Boxing)
- Jarrell Miller (Boxing)
- Jason Cunningham (Boxing)
- Jason Moloney (Boxing)
- Jason Quigley (Boxing)
- Jason Sanchez (Boxing)
- Jason Welborn (Boxing)
- Javier Fortuna (Boxing)
- Javier Molina (Boxing)
- Jayson Mama (Boxing)
- Jazza Dickens (Boxing)
- Jeanfield Swifts (Football)
- Jeddah (Football)
- Jeff Horn (Boxing)
- Jeff Ofori (Boxing)
- Jeison Rosario (Boxing)
- Jeremiah Nakathila (Boxing)
- Jeremias Ponce (Boxing)
- Jermaine Franklin (Boxing)
- Jermall Charlo (Boxing)
- Jermell Charlo (Boxing)
- Jerry Forrest (Boxing)
- Jersey (Cricket)
- Jersey Reds (Rugby Union)
- Jersey Under-19s (Cricket)
- Jersey Women (Cricket)
- Jerwin Ancajas (Boxing)
- Jesse Hart (Boxing)
- Jesse Rodriguez (Boxing)
- Jessica Camara (Boxing)
- Jessica McCaskill (Boxing)
- Jessie Vargas (Boxing)
- Jeunesse D'Esch (Football)
- Jharkhand (Cricket)
- Jharkhand Women (Cricket)
- Jiangsu Suning FC (Football)
- Jimmy Kilrain Kelly (Boxing)
- JK Trans Narva (Football)
- JL Bourg (Basketball)
- Joburg Super Kings (Cricket)
- Joe Cordina (Boxing)
- Joe Fournier (Boxing)
- Joe Joyce (Boxing)
- Joe Smith Jr (Boxing)
- Joet Gonzalez (Boxing)
- Johann Duhaupas (Boxing)
- Johannesburg Buffaloes (Cricket)
- John Gotti III (Boxing)
- John Riel Casimero (Boxing)
- John Ryder (Boxing)
- Johnny Fisher (Boxing)
- Jon Fernández (Boxing)
- Jon Jones (Mixed Martial Arts)
- Jonathan Gonzalez (Boxing)
- Jono Carroll (Boxing)
- Jordan (Football)
- Jordan (Basketball)
- Jordan (Tennis)
- Jordan Gill (Boxing)
- Jordan Thompson (Boxing)
- Jorge Linares (Boxing)
- Jorge Masvidal (Boxing)
- Josber Perez (Boxing)
- José Benavidez Jr. (Boxing)
- Jose Pedraza (Boxing)
- José Ramirez (Boxing)
- Jose Uzcategui (Boxing)
- Jose Zepeda (Boxing)
- Joseph Diaz Jr (Boxing)
- Joseph Jackson (Boxing)
- Joseph Parker (Boxing)
- Josh Kelly (Boxing)
- Josh Taylor (Boxing)
- Josh Wale (Boxing)
- Josh Warrington (Boxing)
- Joshua Buatsi (Boxing)
- Joshua Franco (Boxing)
- Jovanie Santiago (Boxing)
- Jozi Stars (Cricket)
- Juan Diaz (Boxing)
- Juan Francisco Estrada (Boxing)
- Juan Macias Montiel (Boxing)
- Julian Williams (Boxing)
- Julio César Chávez Jr. (Boxing)
- Julio Cesar Martinez (Boxing)
- Junior Fa (Boxing)
- Junto Nakatani (Boxing)
- Jupiter Links Golf Club (Golf)
- Justis Huni (Boxing)
- Juventus (Football)
- Juventus Femminile (Football)