Pablo Sebastián Álvarez Valeira (born 17 April 1984 in San Martín, Buenos Aires) is an Argentine former football player, who played as a defender.

During the 2003–2004 Argentine season, the young defender continued to play in the youth ranks, but made 4 first team appearances, and in 2004 he won his first title by helping Boca to win the Copa Sudamericana.

In July 2005 Álvarez surprisingly left Boca Juniors to join Estudiantes de La Plata, where he won the second title of his career.

Following his impressive displays during the 2006–07 season, he was linked with a host of European clubs, but remained at Estudiantes over the summer transfer window, making an additional 15 appearances for his club In January 2008, however, Álvarez joined Sicilian giants Calcio Catania in the Italian Serie A, teaming up with former teammate Matias Silvestre, who also transferred to Catania in January 2008, from Boca Juniors.

Catania also notably defeated Juventus, in a season, that the team reached a record points total in the Serie A, finishing in 13th position, also making it to the semi-finals of the 2009–10 Coppa Italia.