Thompson, 26, was shortlisted for this season's Championship player-of-the-year award. He is a former member of Gloucester's academy.
"Guy has made a lot of people sit up and take notice with his performances in the Championship this season," said Wasps rugby director Dai Young. "He is an explosive runner who will scare defences with his pace and power. His ability to play across the back row will be very valuable and we are all looking forward to seeing what he can do at this level."
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