Former England captain Chris Robshaw will play for the Barbarians against England at Twickenham prior to joining San Diego Legion in the United States.
The Quilter Cup game on 25 October is set to be Robshaw's last in England before his move.
The flanker led Harlequins to victory against Leicester on his farewell appearance for the club on Sunday.
"It will be great fun and a great challenge to face up against old team-mates and I can't wait," said Robshaw.
Robshaw won 66 caps for his country before retiring from the international game following the tour of South Africa in 2018.
"It has been a strange season and while I have not been able to play out my Quins career in front of fans, I am so happy I will have a chance to say farewell to England at Twickenham," he added.
"The opportunity to get back out there at HQ, this time in a Barbarians shirt, and facing Eddie [Jones'] England will be just incredible for me.
"It's been a very emotional end to the season and I'm so honoured to have the opportunity to be part of the return of the game to Twickenham and to the international stage.
"Becoming a Barbarian will be a very special moment and a very special memory for 2020."