The 2012 Summer Olympics, formally the Games of the XXX Olympiad and commonly known as London 2012, was an international multi-sport event that was held from 27 July to 12 August 2012 in London, United Kingdom. The first event, the group stage in women's football, began on 25 July at the Millennium Stadium in Cardiff, followed by the opening ceremonies on 27 July. 10,768 athletes from 204 National Olympic Committees (NOCs) participated.