The CBGB actor will carry the flame from Middlesex University on Wednesday, July 25 in the lead-up to the Games.
"It's really exciting. I've always been a big fan of the Olympics and [have] always [wanted] to get involved with it," Grint told MTV News.
"It's a really historical kind of event, and I don't think in my lifetime there'll be another Olympics in London, so yeah, I feel really honoured to be part of it."
He also shared his favourite sports to watch during the global sporting competition, adding: "I like all the athletic and track kind of events. I like the hammer throw; all the weird ones [are] pretty cool."
Grint is one of many celebrities to carry the Olympic torch, following the likes of Doctor Who star Matt Smith, gold medal winning athlete Michael Johnson and Black Eyed Peas frontman and The Voice UK coach will.i.am.