The Welsh flag will be proudly flying over the stadium as Team GB's women play New Zealand in the first match of the Games, followed by Brazil Vs Cameroon.
11 football matches will be played over 16 days at the Millennium Stadium, providing a boost to tourism and businesses. The First Minister Carwyn Jones and Sports Minister Huw Lewis will be attending the opening matches.
The First Minister said:
"The Olympics are the greatest show on earth and today we will see the very first sporting action taking place here in Wales and it is great that we are part of this global event. In two days the eyes of the world will focus on the opening ceremony in London, but today Wales is in the spotlight and once again we have an opportunity to show people across the globe what a fantastic host we are for top sporting events."
Heritage Minister Huw Lewis added:
“It is an honour for us to be hosting the first sporting event in the 2012 Games. The football matches taking place are a great opportunity for the people of Wales to experience Olympic competition in our capital city. Wales will also benefit from the global TV exposure of the Millennium Stadium as an Olympic venue as these matched are beamed into homes across the world."