Mario Roberto Viera Gil (born 19 October 1959) is a Uruguayan football manager and former player who played as a goalkeeper.
Born in Florida, Viera only represented clubs in his home nation as a player, notably being a part of the Bella Vista squad who featured in the 1981 Copa Libertadores.
In 2000, after a year as an assistant at Independiente Petrolero, Viera made his managerial debut while in charge of Chinese club Tianjin Lifei in the China League Two.
He returned to his hometown in 2001 to manage Atlético Florida, but was later in charge of another Chinese club, Tianjin Mingte, in 2002.
Viera returned to work as an assistant of Pelusso at Cerro, Danubio and Alianza Lima before being appointed manager of Universidad César Vallejo in 2008.