O'Connell was selected in Ireland's 2011 Six Nations Championship squad, playing against Italy, France, Scotland, Wales and England. He was selected in Ireland's 2011 Rugby World Cup training squad for the warm-up tests in August 2011. He played in both tests against France, captained Ireland in their final warm-up Test against England and was selected in Ireland's 30-man squad to go to New Zealand. Ireland won their opening pool game against the USA, with O'Connell being awarded Man of the Match. He started in Ireland's historic 6–15 victory against Australia, their first win against Australia at a World Cup. O'Connell also started against Italy in Ireland's final pool game. His World Cup ended when Ireland were defeated 22–10 against Wales in the quarter-final.