At the World Cup Williams was partnered with Matthew Stevens to represent Wales, and they reached the semi-finals, losing 1–4 against China. Williams then reached the final of the Australian Goldfields Open, but lost 8–9 against Stuart Bingham, after leading 8–5 at one point of the match. Williams also lost from a winning position in the final of the next major ranking event, the Shanghai Masters. His run included a 6–5 win over Neil Robertson in the semi-final, and he led Mark Selby 9–7 in the final, but lost the last three frames to lose 9–10. The defeat also meant that Selby took the world number one spot from Williams. He was beaten in the last 16 of the 2011 UK Championship by Ricky Walden and reached the quarter-finals in his defence of the German Masters, where he succumbed 3–5 to Stephen Lee. Williams suffered a 1–5 defeat to Mark King in the first round of the World Open and by the same scoreline to Ronnie O'Sullivan in the second round of the China Open.