The 23-year-old defender has been named by Stuart Pearce in the 18-man squad to compete for a gold medal.
“I am just delighted to have been included and obviously it is a great honour to be selected for such an occasion as the Olympic Games,” Tomkins told the official site.
“A lot of the boys I have played with before with England so it will be good to spend some time with them again.
“It will also be great to play alongside Craig Bellamy again. He’s a great player and a proper character. Ryan Giggs is a legend of the game so it would be fantastic to play alongside him too.
“Obviously I will miss some of the pre-season but I will be training every day and hopefully playing regularly. With an 18-man squad there should be chances for everyone to play.
“It’s the first time in more than 50 years that Team GB has taken part in the Olympics so it is something I and all the other players I am sure are looking forward to.
“I am grateful to West Ham for giving me the opportunity to represent Great Britain at the Olympics and I’ll do my very best to represent the Club.”