DOB 8th March 1972
Turned professional 1991
Ranking tournament victories One - British Open 1999
Money list earnings 2012/13 + 2013/14: £111,263
Highest Tournament Break 143 - B&H Championship 1991
O'Brien reached his first professional final in seven years with an excellent run at the 2014 Gdynia Open in Poland.
He won six matches at the European Tour event, beating the likes of Alan McManus and Dominic Dale. But he was denied the trophy by Shaun Murphy, losing 4-1.
An impressive 2013/14 season also saw O'Brien reach the last 16 of the Australian Goldfields Open and International Championship. But it finished in disappointment as he lost 10-9 on a respotted black against Robbie Williams in the final qualifying round of the World Championship.
The Irishman reached his first ranking event final in eight years with a brilliant run at the 2007 Northern Ireland Trophy in Belfast.
He scored a superb 5-4 win over John Higgins, finishing with two century breaks. O'Brien went on to beat Barry Hawkins, Mark Allen and another of snooker's big guns - Ronnie O'Sullivan - to earn his final place.
He battled hard against Stephen Maguire but could manage only five frames in the best-of-17 encounter. "I felt great and I still enjoyed it. I hope this is the norm for me now and I don't have to wait eight years for my next final. Some people pigeon-hole me as a boring plodder but I hope I have shown this week that I'm more than that," said O'Brien.
O'Brien had double cause for celebration during the 1998-99 season as he claimed his first major title and secured his place among the top 16 for the first time. He showed all his battling qualities in the 1999 British Open, winning four of his six matches in the deciding frame then overcoming Anthony Hamilton 9-7 in the final.
In 2001, O'Brien came within one frame of winning the Masters at Wembley Conference Centre. Victories over Mark Williams, Ken Doherty and Dave Harold took him through to the final and he then led Paul Hunter 7-3 before losing a superb match 10-9 some 30 minutes after midnight.
He loves golf and names Ben Hogan one of his all-time heroes; once paraphrasing the nine-time major winner by saying: "Snooker's not what I do. It's who I am."
He is also an enthusiastic runner with Lucan Harriers. He and wife Jean have a daughter called Isobel.
Ball by ball scoring and results from tournaments