Wentzel, a former South Africa Test player, left Leeds last week following their relegation from the Aviva Premiership, and the experienced lock becomes Wasps' 10th new signing for next season.
He was previously with Leicester before moving to Leeds, spending two seasons at each club.
Wentzel said: "It was a hard decision for me to leave Leeds, but I believe it is the best decision for me and the future of the club.
"I really enjoyed my time there and made some great friends. I must thank all my team-mates and the fans for their amazing support the past two years.
"On the other hand, I am really looking forward to join a club with a proud history like Wasps and believe I can play a part to get them back where they belong at the top of English and European rugby."
Wasps chief executive Chris Thomas added: "Marco will be a fantastic addition to our pack for next season.
"He has much-admired leadership qualities and we know that he is considered a fantastic professional in how he carries himself on and off the pitch."
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