Kriel, who has won 11 Springbok caps, will join up with his old Lions coach Johan Ackerman, who moved to Gloucester last year.
Gloucester have also signed hooker Franco Marais and lock Gerbrant Grobler from South Africa for next season.
Kriel has been sidelined with a shoulder injury this year and has missed the Lions’ Super Rugby campaign.
“We are always sad to lose a player but to lose a player of this stature hurts the franchise and the industry,” the Lions said in a statement.
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Gloucester Director of Rugby David Humphreys said: "Jaco's record speaks for itself. He will understand immediately what Johan expects from his players, and the style of play that we are trying to promote.”
(Reporting by Mark Gleeson, Editing by Ed Osmond)
