Veteran second-row Nick Kennedy is among seven first-team players leaving Harlequins, the club have announced on Tuesday.
Quins have also confirmed the departures of Maurie Fa'asavalu, Tom Guest, Sam Smith, Nic Mayhew and Max Crumpton with the season now over after last weekend's Premiership semi-final defeat to Saracens at Allianz Park.
Paul Sackey and Tim Molenaar, who were with the club as injury dispensation cover, will also not return.
The retiring Kennedy will return to London Irish, where he spent large swathes of his playing career, making over 200 appearances, taking up a role as Academy Director.
Former Irish teammate Paul Hodgson returns to the Madejski Stadium too as backs coach.
"I have decided to cut short my playing career to be part of the exciting new era at London Irish," said Kennedy.
"I, along with many other past and present international rugby players, am a product of the club's academy.
"I look forward to joining up with the team in the summer, and working with the future stars of the slub."
Hodgson added: "These are exciting times at London Irish and I am thrilled to be part of it.
"The academy has been the essence of the club for a long time and it is a huge part of the new owners' vision.
"It will be an exciting challenge but, with the team that has been acquired, one that we will be up for."