The Tonga international, who played at the 2015 World Cup, will join early in the new season, having most recently been with French side Castres.

The Australian-born forward has also played for Western Force in Super Rugby and made more than 80 appearances for Leicester between 2010 and 2014.

"This is a fantastic opportunity for me to return to England and test myself in the Premiership," Mafi said.

He is the ninth international to join Irish this summer following the club's promotion back to the top flight after one season in the Championship.

Paddy Jackson, Sean O'Brien, Nick Phipps and Waisake Naholo are among the other newcomers.

"We know how demanding and challenging the Gallagher Premiership is, so it is important that we assemble a squad to meet the demands," Exiles director of rugby Declan Kidney told the club website.

"Steve has a wealth of experience and the ability to cover several positions in the second and back row."