Stuart Lancaster has been appointed to the Leinster coaching staff, marking his first full-time return to rugby since overseeing England's ill-fated 2015 World Cup campaign.
Lancaster, who will take on the role of senior coach, arrives at the RDS on a contract until the end of the season, filling a gap in head coach Leo Cullen's team left by the departure of defence coach Kurt McQuilkin.
McQuilkin has returned home to New Zealand to be with his father and sister, who are both ill.
"The sad departure of Kurt McQuilkin due to family reasons has brought about an opportunity to bring in somebody new to the Leinster Rugby coaching team," said Cullen.
"Stuart brings a wealth of experience and is a highly respected figure in world rugby.
"We are all looking forward to having Stuart join our team and together helping the players maximise their potential as a group."
CEO Mick Dawson added: "We are always looking at options around resources but once we were made aware of Kurt's departure, we narrowed our focus and we are delighted that Stuart has agreed to come on board.
"I know, having spoken at length to Stuart, that he is excited by the challenge of getting into club rugby again and the day to day interaction with players."
Lancaster became England coach in 2011 and was at the helm as they became the first host nation to be eliminated from the World Cup at the pool stage, resigning soon after.
Since leaving England, Lancaster has undertaken short-term roles with the Atlanta Falcons, British Cycling, the Football Association and Counties Manukau in New Zealand's Mitre 10 cup.