On 31 May 2016, Williams was named in Coleman's 23-man squad for UEFA Euro 2016, Wales' first major tournament for more than half a century. On 1 July in Lille, Williams headed the equalising goal, against Belgium in the quarter-finals as Wales eventually won 3–1 to progress to the semi-finals for the first time in their international football history. In the semi-final, Wales lost 2–0 to Portugal.