Young's move from Cardiff Blues had been rumoured to have been held up by compensation issues regarding the final year on his contract with the Welsh capital side but Wasps now have their man at long last.
"We are delighted to welcome Dai to London Wasps and we believe he is exactly the right person to take the club forward. Dai brings a wealth of experience to the club and this is an appointment for the long term," said Wasps chief executive Chris Thomas.
"We remain an ambitious club and want to be competing at the highest level. Dai is the person to help us achieve these ambitions.
"Dai has done a sterling job in Cardiff, developing a host of young talent into international quality players as well as building an excellent team with strong spirit. We were hugely impressed with his vision for London Wasps which is in keeping with our key objective of developing sustained long-term success."
Young, who toured with the Lions as a player in three separate decades in 1989, 1997 and 2001, had spent the past nine seasons in Cardiff and had been tipped as a possible successor to Warren Gatland for the Wales job.
But the former prop forward has also spoken about his desire to coach outside of Wales and had previously been a candidate for the Leicester Tigers job.
Young believes the move to Adams Park is an opportunity to broaden his horizons at a club with an impressive history, even if Wasps haven't been synonymous with success over the past two seasons.
"This is an enormous opportunity for me," added Young, who takes over from Leo Holden as Wasps boss following the earlier departure of Tony Hanks.
"I have loved my time with Cardiff but I am looking forward to a new experience in a new environment.
"There is a hugely talented group of players here to work with and the challenge to help get a great club into a position where they are once again challenging for success was too good to turn down."