The playmaker last week revealed he will leave Highlanders and turn his back on the All Blacks at the end of the 2018 Super Rugby season.
Wasps on Monday announced that Sopoaga, capped 16 times by the world champions, will link up with the Coventry-based club for the 2018-19 campaign.
And director of rugby Young felt the opportunity to recruit the 26-year-old was good to pass up.
"When a world-class fly-half became available we jumped at the chance, as that doesn't happen very often," the Welshman stated.