As a youth Cian O'Connor's family moved frequently, and he grew up in County Wicklow, County Kildare, and for some time in Florida in the United States. Encouraged by his father he took up hunting on horseback and his father felt that much of his riding success came from his early training in that sport. O'Connor competed controversially at the 2004 Olympics where he appeared to have won the gold medal, but he and his horse were disqualified for a doping positive on the horse, and he was stripped of the medal. In 2012 he returned to the Olympics to help Ireland win a team jumping bronze medal. O'Connor has been a member of over 90 Irish Nation's Cup teams, has won numerous Grand Prix events, and competed in two World Championships, three European Championships and two Olympic Games. He was a member of the Irish team that won the Aga Khan Trophy in 2004 and 2008 and has won or jointly won the puissance at Dublin Horse Show four times. Cian is based at Karlswood Stables outside Ashbourne, County Meath.