Osvaldo Díaz (born 22 December 1981) is a Paraguayan footballer. He currently plays for 12 de Octubre.
Díaz began his career at Club Guaraní before moving in mid 2007 to Olimpia Asunción in the Paraguayan First Division.
On 1 February 2008 he was signed by AC Lugano, where he only played a total of 17 minutes in 3 games.
Diaz was part of the silver medal-winning Paraguayan 2004 Olympic football team, which earned a quarter-final place with two victories in the qualifying round. Having finished second in the league, the squad later beat South Korea in the quarter-finals, and Iraq in the semi-finals, before losing to Argentina in the final.