The 23-year-old, who has made more than 100 appearances for Wales on the World Sevens circuit, is one of two Welshmen in the 12-man squad, with Scarlets flanker James Davies the other representative.
Final preparations are being made at a training camp in Belo Horizonte, with Great Britain set to kick off their campaign against Kenya on Tuesday.
It is an opportunity Cross is relishing as rugby appears at an Olympic Games for the first time since 1924, and he is eagerly awaiting the start of competition.
“Obviously as rugby players we realise that this is an opportunity no-one has had for a very long time and we want to make the most of it,” said Cross, who has played his 15-a-side rugby for Newport RFC over the last two seasons.
“We have worked really hard in the build-up, there have been some hard days and the selection process has been physically and mentally challenging.
“It means a lot to make the final cut, growing up as a boy in Brynmawr I don’t think appearing at the Olympics was something I ever expected to achieve.
“We know we are in a tough group. New Zealand are a strong side but Kenya have shown real progress over the last few years and Japan showed at the Rugby World Cup that they are a force to be reckoned with.
“It will be tough but we feel we have the ability to do well, I know a lot of the guys well from the international circuit and I cannot wait to get started now.”
