He is a four-time World Snooker Champion, and has won the Masters three times and the UK Championship twice for a total of nine Triple Crown titles, putting him on a par with John Higgins, and behind only Ronnie O’Sullivan (23), Stephen Hendry (18) and Steve Davis (15).

[5] In April 2003, aged 19, he reached his first ranking final at the Scottish Open, where he finished runner-up to David Gray,[6] earning himself a place in the top 32 for the first time.

[2] In October 2004, he made it to the quarter-finals stage of the 2004 Grand Prix with a 5–3 win over Peter Ebdon,[7] but there he was whitewashed 5–0 by Ronnie O'Sullivan,[8] the tournament's eventual champion.

[30] However, he could not reproduce his Crucible success from the previous season; despite going into the 2008 World Championship as one of the bookmakers' favourites for the title, Selby was defeated 8–10 in the first round by Mark King.

[40] At the 2011 China Open, he beat Tian Pengfei, Robert Milkins, Ali Carter, and home favourite Ding Junhui, but was defeated 8–10 by Judd Trump in the final.

[2] He also won the minor-ranking PTC Event 4 (the 2011 edition of the Paul Hunter Classic); having edged out Ronnie O'Sullivan 4–3 in the semi-finals, he achieved a 4–0 whitewash over Mark Davis in the final.

[60][61] Selby lost his world number one ranking on 2 November 2012, when Trump claimed the top spot by reaching the final of the inaugural International Championship in China.

[76] At the China Open, Selby became the fourth player in history to miss the final black on a 147 attempt, and only the second – after Ken Doherty – to do so in a televised match, in a 5–1 defeat of Mark King.

[88] Defending his title at the UK Championship in December, Selby compiled snooker's 100th officially recognised maximum break in professional competition,[89] in the seventh frame of his semi-final against Ricky Walden.

[112] He made an unexpected early exit from the ranking International Championship, when he was eliminated in the last 128 by 19-year-old tour rookie Oliver Lines, who had recovered from 0–4 behind to defeat him 6–4.

[115] In his first-round encounter with Shaun Murphy at the Masters in January, Selby fell 1–5 behind before recovering to draw level at 5–5, but then lost the match in the deciding frame.

[134] Returning to the tour at the World Championship in April, he beat Robert Milkins 10–6, Sam Baird 13–11, and Kyren Wilson 13–8, to face Marco Fu in the semi-finals.

[141] At the UK Championship, he defeated John Higgins 6–5 in a high-quality quarter-final match that lasted five hours; Selby won on the colours in the deciding frame.

[142] After despatching Shaun Murphy 6–2 in the semi-finals,[143] he developed a 7–2 advantage over Ronnie O'Sullivan in the final of the event, which decreased to 7–4, followed by four breaks of 130 or more over the next five frames—two by each player—bringing the score to 9–7 in Selby's favour.

[150] He failed to progress past the fourth round of the Paul Hunter Classic in defence of his title, losing 1–4 to eventual champion Michael White.

[169] O'Sullivan reclaimed the top spot by winning his 36th ranking title at the Tour Championship;[168] Selby had himself been eliminated in the first round by Neil Robertson in a final-frame decider, after squandering a four-frame lead.

[170] He had an opportunity to regain the top spot at the China Open less than two weeks later, but lost 3–6 to Craig Steadman in the qualifying round which had been held over from the original qualification stage in February.

[172][173] As a result of this mediocre performance, he ended the season as world number six, having also been outranked by John Higgins, Neil Robertson, Mark Williams and Judd Trump.

[187] He also qualified for the Players Championship, based on the one-year ranking list; in the first round, he whitewashed Mark Williams 6–0,[188] but was then knocked out in the quarter-finals by Stephen Maguire in a deciding frame 5–6.

[203] After defeating Fan Zhengyi, Chang Bingyu, Liang Wenbo, Hossein Vafaei and Zhou Yuelong, he lost 5–6 to Neil Robertson in the semi-finals.

[210] In December, after yet another loss to Robertson at the quarter-finals of the 2020 UK Championship,[211] Selby successfully defended his Scottish Open title, beating Yuan Sijun, Nigel Bond, Mark Joyce, Lyu Haotian, Ricky Walden and Jamie Jones to reach the final, then defeating Ronnie O'Sullivan 9–3 to claim his 19th ranking tournament win, and his third Home Nations Series trophy, becoming the second player, after Judd Trump, to win three Home Nations events.

[212] The following week, he reached the semi-finals of the 2020 World Grand Prix, where he was defeated 4–6 by Jack Lisowski, despite compiling the highest break of the tournament, a 143 in the seventh frame of the match.

[213] Selby reached the final of the 2021 Snooker Shoot Out in February, but his early 24-point lead was eclipsed by Ryan Day's 67-point winning break in the last four minutes of the match.

[248] During the first half of the season, Selby has missed out on the 2023 Northern Ireland Open, as he—along with Ali Carter, John Higgins, Thepchaiya Un-Nooh and reigning world champion Luca Brecel—opted not to enter, so he could play at an exhibition event in Macau, China instead, originally scheduled to take place from 27 to 29 October.

[249] Following negotiations, the Macau exhibition was rescheduled to be played from 22 to 24 December, and the WST granted the concerned players permission to participate; however, they remained absent from the Belfast tournament, as they had not entered it.

[251] In January, Selby exited both the 2024 Masters and the 2024 World Grand Prix at the quarter-finals stage, losing 5–6 to Mark Allen in the former,[252] and 1–5 to Judd Trump in the latter tournament.

[256] In the next event, the 2024 World Masters of Snooker, he was a quarter-finalist, but suffered a 3–4 loss to Mark Allen after leading 3–1, but spoiling his match-winning chances by missing the black off its spot twice in the next two frames.

[257] The following week, Selby won the 2024 Championship League by defeating Joe O'Connor 3–1, lifting his first trophy of the season, almost a year after his last tour event success.

[126] Selby is also a fan of darts and has played in exhibition matches at Ibstock in Leicestershire, beating Eric Bristow in 2007 and taking on Raymond van Barneveld in 2009.

In June 2006, he won the WEPF World Eightball Championship at the Norbreck Castle Hotel in Blackpool, beating Chris Melling 10–5 in the semi-finals and Darren Appleton 11–7 in the final.