During the 2007 Rugby World Cup, Williams earned his 50th cap against Japan. He scored two tries in that match, temporarily putting him on top of the 2007 Rugby World Cup try-scoring table with a total of five tries. The tries also put him above Ieuan Evans on the all-time Wales try scoring list, trailing only Gareth Thomas at that time. His try against France in their 2008 Six Nations Championship decider on 15 March 2008 placed him joint eighth on the all-time Test try scoring list with Thomas, and surpassed Thomas on the all-time Wales try scoring list.