Mark Selby in the last 64. In the first round of the Masters, Selby played against Mark Willams in a repeat of the 2017 edition. However, it was Williams who prevailed in their encounter 6–5. It was also the second time that Selby lost in a deciding frame at the tournament. Selby retained his China Open title, defeating Barry Hawkins 11–3 in the final. It was the 3rd China Open title he won in 4 years. Selby's two-year reign as World Champion came to an end at the first round of the 2018 World Snooker Championship. Facing Joe Perry, Selby trailed 2–7
Mark Selby rookie Oliver Lines came from 0–4 behind to defeat him 6–4. In the invitational Champion of Champions tournament, he reached the quarter-finals, but lost 1–6 against Judd Trump. He suffered another early exit at the UK Championship when he lost 4–6 to David Morris in the last 64. Playing Shaun Murphy in the first round of the Masters, Selby fell 1–5 behind before recovering to 5–5, but lost the match 5–6 on the deciding frame. It was the first time that Selby lost in a deciding frame at the Masters, having won the previous 11 deciding frames. At the German