Infobox last updated on: 16 February 2009.

Mario Ančić (born March 30, 1984) is a professional tennis player from Croatia. He has won three singles titles and five doubles titles. His highest international ranking came during the 2006 ATP Tour, when he reached No. 7 in singles. Apart from his success on the ATP Tour, Mario helped Croatia to win the 2005 Davis Cup and at the Athens Olympic Games in 2004, he and Ivan Ljubičić won a bronze medal in doubles for Croatia.

As a teenager making his Grand Slam debut at the 2002 Wimbledon Championships, he defeated 7th-seeded Roger Federer. This win also made him the last player to defeat Federer at Wimbledon (until Rafael Nadal) and on grass courts; and during the years, he was known as the last man to beat Federer, until Nadal's victory over Federer in the 2008 Wimbledon Championships finals. His best performance at Grand Slams came at the 2004 Wimbledon Championships, when he reached the semifinals. Due to his success at Wimbledon and grass courts, many saw in Mario a successor of Goran Ivanišević, the 2001 Wimbledon Champion and a former No. 2 in singles, earning a nickname New Goran and Baby Goran.