The 29-year-old centre has won 19 caps for the Springboks since making his try-scoring international debut against Wales on 5 June 2010. Watch here
De Jongh has returned from injury this season to earn inclusion in the South Africa A squad to face the French Barbarians in June.
Ahead of his move to the UK, De Jongh said: “I can’t wait to play for such an amazing club as Wasps in the Aviva Premiership and am relishing the ultimate challenge that lies ahead.
“Wasps has an incredible pedigree and some phenomenal players, and working with everyone there is going to help me improve my game.
“From everything I’ve heard, Wasps sounds like a fantastic place and a perfect fit for any top end athlete to be.
Having watched their last couple of games, I believe there is a lot to look forward to at the club.”
Speaking about the Springbok centre, Wasps’ director of rugby Dai Young said: “We are really pleased to have Juan coming on board next season.
“He has a good eye for a gap and plenty of pace which makes him dangerous in attack, while he also has strong organisational skills in defence.
“Juan’s international experience and his ability to play 12 and 13 will also benefit the squad, with Kurtley [Beale] returning to Australia to further his Wallaby career, Nick [De Luca] retiring and Alapati [Leiua] moving to Bristol.
“Juan and Gaby Lovobalavu’s arrival will add to the talented group of centres we have at the club.”