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|Born||March 23, 1976|
Rio de Janeiro, Brazil
|Rank||6th Degree Black Belt in Brazilian Jiu-Jitsu|
|Years active||1997–2013; 2017|
|2003 São Paulo, Brazil||-66kg|
|2005 California, USA||-66kg|
|2007 New Jersey, USA||-66kg|
|2011 Nottingham, UK||-77kg|
|1997 Rio de Janeiro, Brazil||-76kg|
|1998 Rio de Janeiro, Brazil||-76kg|
|2000 Rio de Janeiro, Brazil||-76kg|
|Pan American Championship|
|2002 California, USA||-69kg|
|2004 California, USA||-69kg|
Leo Vieira began training Jiu-Jitsu at a very young age. He has won numerous medals, such as the Brazilian Jiu-Jitsu World Championships, Pan American Championships and the prestigious ADCC world championships. After being on break from Jiujitsu Gi competition, Vieira competed again on July 16, 2017 at the age of 41. He competed in Absolute Championship Berkut Jiu-Jitsu 6 in Moscow and lost the fight via terra footlock. On September 25, 2017, Vieira competed in the ADCC against former Ultimate Fighting Championship title contender, Chael Sonnen in the absolute division. Vieira lost the fight via referee's decision.
CheckMat Jiu-Jitsu Team
One of the most successful teams in contemporary Brazilian Jiu-Jitsu, CheckMat's worldwide headquarters is in São Paulo, Brazil. CheckMat was established in 2008 by Leo and his brothers. Since its creation, Checkmat has become one of the top teams in Brazilian Jiu-Jitsu. Team CheckMat is the 2008 and 2009 NoGi World Champion Team. Team Checkmat also came in first for the Brazilian Nationals (Gi) 2010  and Brazilian Nationals (No-Gi) 2010.
- Gracie Mag Brazilian BJJ Nationals 2012 "In the stands Fábio Gurgel, Léo Vieira, Ramon Lemos, Rodrigo Cavaca and André Marola represented some of the traditional powerhouse teams that were in the running."
- "BJJ Legend Leo Vieira Returns to Competition at 41 Years of Age". BJJHeroes.com.
- Djokovic, Iva (27 June 2017). "Leo Vieira Returns to Competition at Age 41". Bjjee.com.
- Cruz, Guilherme (24 September 2017). "ADCC 2017, Day 2 results: Chael Sonnen defeats Leo Vieira". MMAFighting.com.
- "Checkmat conquista o bi no Mundial No Gi". Archived from the original on March 11, 2012. Retrieved March 29, 2012.
- Carlos Eduardo Ozório. "No-Gi Brazilian Nationals decisive day". Graciemag.com. Retrieved 2015-12-12.
- Carlos Eduardo Ozório. "Brazilian team champion issues provocation: "The dream of the grand slam is over"". Graciemag.com. Archived from the original on 2012-03-03. Retrieved 2015-12-12.
- "Leonardo "Leozinho" Vieira". BJJHeroes.com. Retrieved May 7, 2019.