John Kingston will take over from Conor O'Shea as director of rugby at Harlequins from next season.
O'Shea will end a six-year relationship with Quins when he takes over the reins from Jacques Brunel as head coach of Italy at the end of the campaign.
The club, who still have slender hopes of achieving a play-off position in the Premiership and will contest the Challenge Cup final against Montpellier on May 13, have opted to go with an internal appointment, promoting Kingston from his position as head coach.
"I'm immensely proud of what I have achieved in the last eight years as head coach and taking the role of director of rugby is an exciting and well-timed new challenge for me," Kingston said in a statement.
"Conor O'Shea will leave a lasting legacy on this club with the success we have achieved over the last six years and it is something I am excited to build on heading into our 150th year.
"He has made a massive impression on me, the squad, staff and supporters and we know he will be greatly missed by the whole club.
"I'm looking forward to getting the best out of a great group of players and a wonderfully exciting new coaching group during the next era for Harlequins."
Replacing Kingston as head coach will be Mark Mapletoft, who had six years as backs coach.
Graham Rowntree will join as forwards coach after an eight-year spell with England came to an end following Eddie Jones' appointment, while Nick Easter will join the coaching team and take charge of defence.