|Full name||Mario Sebastián Viera Galaín|
|Date of birth||7 March 1983|
|Place of birth||Florida, Uruguay|
|Height||1.85 m (6 ft 1 in)|
|* Senior club appearances and goals counted for the domestic league only and correct as of 00:00, 31 March 2014 (UTC).
† Appearances (Goals).
Born in Florida, Florida Department, Viera started his professional career with Club Nacional de Football. After one sole season he was expected to move to Premier League club Arsenal in August 2005, but its manager Arsène Wenger withdrew from the deal when the player did not pass the medical.
Eventually Viera signed with Villarreal CF in Spain, moving alongside Mariano Barbosa (also a goalkeeper) on a four-year contract. He would be an undisputed starter in the following two seasons, although he missed both legs of the 2005–06 UEFA Champions League semifinals against Arsenal.
Viera eventually lost his job midway through the 2007–08 campaign to newly signed Diego López, and never regained it again – no La Liga games in 2008–09 – being released in July 2009. On 11 November he signed a one 1/2-year contract with Greek side AEL 1964 FC, being made eligible to play however only in January 2010; late into that year his contract was terminated, and he joined Junior Barranquilla shortly after.
Viera made his debut for Uruguay on 18 July 2004 in a Copa América quarterfinal match against Paraguay, having been called as a late replacement for starter Fabián Carini, injured. He also featured in the penalty shootout loss against eventual winners Brazil.
Viera's father, also named Mario, was also a professional footballer – and a goalkeeper.