Jerry Sexton has signed a permanent contract with London Irish following a loan spell with the club last season.
The 23-year-old back row joined from Exeter in February but was unable to prevent Irish's relegation to the Championship in his six appearances.
"I'm really looking forward to helping the club achieve promotion back to the Premiership at the first time of asking," he said.
An Ireland Under-20 international, Sexton is a Leinster academy graduate.
He is the younger brother of Ireland fly-half Johnny Sexton.