| Joel Theissen | |
| Fullname: | Joel Theissen |
| Birth Date: | 1985 8, df=yes |
| Birth Place: | Windsor, New South Wales, Australia |
| Position: | Midfielder |
| Youthclubs1: | Australian Institute of Sport |
| Collegeyears1: | 2008 |
| College1: | New Mexico Lobos |
| Collegecaps1: | 0 |
| Collegegoals1: | 0 |
| Collegeyears2: | 2009–2011 |
| College2: | Rio Grande RedStorm |
| Years1: | 2003–2004 |
| Clubs1: | Newcastle United Jets |
| Caps1: | 0 |
| Goals1: | 0 |
| Years2: | 2004–2005 |
| Clubs2: | Central Coast United |
| Years3: | 2005–2006 |
| Clubs3: | Parramatta Melita Eagles |
| Years4: | 2006 |
| Clubs4: | Sydney FC |
| Caps4: | 1 |
| Goals4: | 0 |
| Years5: | 2007 |
| Clubs5: | Marconi Stallions |
| Years6: | 2007 |
| Clubs6: | Sydney Olympic |
| Years7: | 2008 |
| Clubs7: | Cape Cod Crusaders |
| Caps7: | 10 |
| Goals7: | 1 |
| Years8: | 2009–2010 |
| Clubs8: | Ottawa Fury |
| Caps8: | 29 |
| Goals8: | 0 |
| Years9: | 2011–2012 |
| Clubs9: | GPS Portland Phoenix |
| Caps9: | 24 |
| Goals9: | 4 |
| Nationalteam1: | Australia U20 |
| Nationalteam2: | Australia U23 |
| Pcupdate: | 1 July 2011 |
| Ntupdate: | 23 May 2009 |
Joel Theissen (born 12 August 1986 in Windsor, New South Wales) is an Australian footballer who last played for GPS Portland Phoenix in the USL Premier Development League.
A left-sided midfielder or defender, Thiessen attended the Australian Institute of Sport, and played with former NSL side Newcastle United, before catching the eye of Sydney FC head coach Terry Butcher. Thiessen was placed on a short-term contract the A-League club in September 2006 to cover for the injured Robbie Middleby, and played in one senior game for the team before leaving to play for Marconi Stallions and Sydney Olympic.
In March 2008 Thiessen re-located to the United States to attend college at the University of New Mexico. After failing to be cleared by the NCAA clearinghouse he moved on to the University of Rio Grande in the NAIA. He played with the Cape Cod Crusaders in the USL Premier Development League during his 2008 collegiate off-season. In March 2009 he signed with the Ottawa Fury for the 2009 Premier Development League season, and played two seasons with the team, before moving to GPS Portland Phoenix in 2011.