Ronald Antonio O'Sullivan (born 5 December 1975) is an English professional snooker player who is one of the most successful players in the history of the sport.
Since turning professional in 1992, he has won five World Championships, a record seven Masters titles, and a record seven UK Championships, setting a record total of 19 titles in Triple Crown tournaments.
He shares the record for the most ranking titles (36) with Stephen Hendry and also holds the record as the youngest winner of a ranking title (1993 UK Championship, aged 17 years and 358 days) as well as the youngest winner of the Masters (in 1995, aged 19 years and 69 days).
In the 2017/2018 season, O'Sullivan won five ranking events in a single season, a record that he shares with Hendry, Ding Junhui and Mark Selby.
His career prize money of over £11 million is the highest amount earned by any player in snooker history.A prolific break-builder, O'Sullivan is the only player to have reached 1,000 career century breaks.
He has also achieved the highest number of officially recognized maximum breaks in professional competition (15), and the fastest competitive maximum break, compiled in a time of 5 minutes and 8 seconds at the 1997 World Championship.
He first became world number one in the 2002/2003 season and held the position for five out of eight seasons, ending in May 2010.
He regained the top ranking in March 2019 after a nine-year absence, the longest time any player has spent between spells as world number one, and held it until August 2019.
O'Sullivan has often been a controversial figure in the sport.
Noted for his unpredictable temperament and his struggles with alcohol, drugs, and depression, he has received many warnings and sanctions from the sport's governing body over his conduct and comments.
He took a prolonged break from the sport during the 2012/2013 season and is known for repeatedly declaring his intention to retire.
Outside his playing career, he has worked as a pundit for Eurosport's snooker coverage, has written crime novels and autobiographies, and has starred in the miniseries Ronnie O'Sullivan's American Hustle.
He was awarded an OBE in the 2016 New Year Honours.