At the flagship venue in Stratford, the PM and school children from a number of East London schools were joined by members of the Olympic Park workforce and the local community.
Mr Cameron said that it was a real honour to turn on the floodlights for the first time.
He added: “Today we’re shining a light on this stadium and the brilliant work that’s been done on the Olympic Park so far. In 2012 a light will shine on all of our country as billions look on. I want the world to see that Britain is a confident, forward-looking country - a great place to live, work, invest and do business.”
The stadium itself is lit by over 532 individual floodlights housed in 15 towers suspended 70 meters above the field of play - in order to meet the high definition TV standards required.
The Olympic Delivery Authority (ODA) has also announced that the installation of the spectator seats has been completed in the Stadium, ensuring that the venue remains on track to be finished more than a year before the Games in the summer of 2012.
Secretary of State for Culture, Media and Sport Jeremy Hunt said: “London’s Olympic Stadium is breathtaking. Seeing it lit up, like it will be for 2012 and beyond, is incredibly exciting. The switching on of the lights is a huge milestone in our preparations for what will be a fantastic Games in 2012.”