Óscar Julián Ruiz Acosta (born 1 November 1969 in Villavicencio) is a Colombian football former referee and current referee instructor. He is also a lawyer.
He had been a referee since 1 January 1995, and his international debut was on 12 July 1995 (Paraguay vs. Venezuela). He officiated in the 2002, 2006 and 2010 FIFA World Cups.
His decision was criticized in the Netherlands vs. Côte d'Ivoire match in 2006, which the Dutch won 2–1.
He was preselected as a referee for the 2010 FIFA World Cup and notoriously sent off Yoann Gourcuff in the France vs. South Africa match.
FIFA appointed Ruiz as a referee instructor and member of CONMEBOL's referee assistance program.