Tomás O'Leary (born 22 October 1983) is an Irish former rugby union player who played as a scrum-half. O'Leary played most of his career in the United Rugby Championship with Munster, where he was part of the team that won the Heineken Cup in 2006 and again in 2008. He also played in the English Premiership with London Irish, and the Top 14 with Montpellier. Internationally, he represented Ireland, where he was a member of the team that won the 2009 Six Nations Championship and Grand Slam. Also in 2009, he was selected for the British & Irish Lions, though injury prevented him from touring with the squad. O'Leary retired from professional rugby in July 2017.