O'Neill was born in
Dublin, but brought up in
Monkstown,
County Cork. His uncle was a trainer, and his family had always been interested in racing. He was a skilled
showjumper in his youth, and also rode 24 winners in pony races. He moved to Britain aged 17 and spent his early career riding for
Richard Hannon Sr. His first winner was Port Sunlight, at
Sandown Park on 15 July 1993. Winners were slow to come, and in his first three seasons, he only rode seven. His career took a step forward in 1996 when he won the
apprentice jockeys’ championship with 67 wins. For Hannon, he won several big sprint races on Bold Edge, including the
Cork and Orrery Stakes at
Royal Ascot and the
Diadem Stakes in 1999 and his first
Group 1, the
Prix Maurice de Gheest in August 2000. He also won the
Jersey Stakes at the 1999 Royal Ascot on Lots of Magic. 2003 was his most successful year with 110 winners. These included Airwave in the Group 2
Temple Stakes for Henry Candy, and another
Royal Ascot winner, Macadamia in the
Royal Hunt Cup for
James Fanshawe. In total, he won over £1.3 million in prize money during the year. It was five years before he reached 100 winners or £1 million in prize money again, aided by wins in the
Stewards' Cup for
William Haggas on Conquest I. He spent a period as stable jockey to Henry Candy. Then, in October 2012, he was appointed second jockey to
Sheikh Hamdan al Maktoum, behind Paul Hanagan. The Maktoum partnership led him to the biggest prize of his career – the first
Commonwealth Cup at
Royal Ascot in 2015 on
Muhaarar trained by Charlie Hills. On Mukhadram he finished third in the 2014
King George VI and Queen Elizabeth Stakes. By the end of 2017, he had nearly 1,700 career victories in Britain, and became the seventh most prolific winner among current jockeys on the retirement of
Jimmy Fortune. O'Neill announced his retirement from riding in March 2024. He had suffered serious injuries in a fall at
Wolverhampton in July 2023 and was forced to retire on medical grounds. He rode 1,889 winners in Great Britain. ==Statistics==