Aiden O'Brien was born 16 October 1969 in County Wexford, Ireland. Since 1996, he has been the private trainer at Ballydoyle Stables near Cashel in County Tipperary for John Magnier and his Coolmore Stud associates. O'Brien first started working professionally with horses at P.J. Finn's racing stables at the Curragh, Co. Kildare, and then with Jim Bolger at Coolcullen, Co. Carlow. He has won virtually every major fixture in Europe as well as the 2005 Arlington Million with Powerscourt, the 2001 Breeders' Cup Juvenile with Johannesburg, the 2009 Breeders' Cup Marathon, the 2002 and 2003 Breeders' Cup Turf with High Chaparral, Arlington's Secretariat Stakes in 2000 with Ciro. He won the 2011 Million with Cape Blanco and the 2011 Secretariat the same afternoon with Treasure Beach.