Matt Toomua will put his international ambitions with Australia on hold and move to Leicester Tigers at the end of the 2016 Super Rugby season.
Brumbies playmaker Toomua was part of the Wallabies' Rugby World Cup squad this year, but has agreed a switch to England that will make him ineligible for Australia duty.
Toomua will spend one further season with the Brumbies, before ending his lengthy association with the club to join the Tigers.
"It's a great opportunity for me to be a part of such a successful organisation with such a proud history," said the 25-year-old, who can play at fly-half and inside centre.
"After meeting with [director of rugby] Richard Cockerill and [head coach] Aaron Mauger, I feel very fortunate to be able to further develop as a rugby player in such a great environment and hope to contribute to the club's future success."
Cockerill added: "It is no secret we have been looking to sign a top-class player to add to our backline resources and Matt is certainly in that category.
"He is still a young man but has already achieved such a lot in Super Rugby and played extensively in Test rugby for the Wallabies [earning 23 caps].