Will has represented Wasps in top class rugby since 1995. During that time he has collected four senior England caps, two domestic Cup winners' medals, three Premiership titles and a Heineken Cup winner's medal, including last year's Zurich Premiership and Heineken Cup double.
Green said: "I'm very excited about joining such a top class outfit as Leinster. They are a top European side with many great players - six selected for the Lions says it all. I'm looking forward to experiencing a different way of doing things at one of the big Irish province teams and I hope I can get over there, get my head down and work hard and win silverware.
I've signed a two year deal with the club which gives Charlotte, me and our young son Arthur a change of lifestyle. Having lived in London for 9 years, we're ready for a change. I'm ready on the professional front for a new challenge, and on a private front my family and I are going to have an adventure, enjoying a different culture."
Leinster Chief Executive Mick Dawson added: "Leinster Rugby are delighted to welcome Will and his family to Ireland. Will is a top quality English forward and he has played an integral part in Wasps' recent success. I am confident that he will give added value to our squad for the seasons to come."