The announcement was made on the player’s 25th birthday, with Stormers coach John Dobson saying: “Warrick has established himself as one of the most dynamic backline players in South Africa.
"So we could not be more thrilled to have him on our books going forward.
"With Dillyn Leyds leaving, we couldn’t have asked for anyone better to step into the 15 jersey.
“I am sure his presence will also have a hugely positive influence on the players around him."
Gelant, whose Bulls contract expires in July, is set to make the No.15 jersey his own, allowing Damian Willemse to concentrate on flyhalf only.
Dobson adds: “We are also looking forward to giving Damian the opportunity to settle at flyhalf going forward, with Warrick providing his trademark strike threat from the back.
“Warrick is a deadly finisher with a wonderful feel for the game and awareness of space, which is just what we need for the talent we already have in the backline to thrive.”
Knysna-born Gelant adds: “I can’t wait to join up with the Stormers and I’m very excited about what the future holds. I want to take my game to new heights and I believe that working with the players and the coaches at the Stormers will help me to do that.”