The Millennium Stadium (Welsh: Stadiwm y Mileniwm) is the national stadium of Wales, located in Cardiff. It is the home of the Wales national rugby union team and has also staged games of the Wales national football team. Initially built to host the 1999 Rugby World Cup, it has gone on to host many other large-scale events, such as the Tsunami Relief concert, the Super Special Stage of Wales Rally Great Britain, the Speedway Grand Prix of Great Britain and various music concerts. It also hosted six FA Cup finals and several other high profile football fixtures whilst Wembley Stadium was being redeveloped.

The Millennium Stadium is owned by Millennium Stadium plc which is a subsidiary company of the Welsh Rugby Union (WRU). The stadium was designed by a team led by architects Bligh Lobb Sports Architecture. WS Atkins were the structural engineers, and the building contractor was Laing. The total construction cost of the stadium was £121 million, of which the Millennium Commission funded £46 million.

The stadium opened in June 1999 and its first major event was an international rugby union match on 26 June 1999, when Wales beat South Africa in a friendly by 29–19 before a test crowd of 29,000. With a total seating capacity of 74,500, it is the third-largest stadium in the Six Nations Championship behind the Stade de France and Twickenham. It is also the second-largest stadium in the world with a fully retractable roof and was the second stadium in Europe to have this feature. Listed as a category four stadium by UEFA, the stadium was chosen as the venue for the 2017 UEFA Champions League Final. On 8 September 2015, the Welsh Rugby Union announced a 10-year sponsorship deal with the Principality Building Society that would see the stadium renamed as the "Principality Stadium" from 1 January 2016.