De Lange, 31, played two Tests, four ODIs and six T20Is for South Africa between 2011 and 2016, but has been playing county cricket regularly over the last six years. He initially signed for Glamorgan as a local player through a spousal visa, but joined Somerset on a two-year deal from the end of the 2020 season after changes to registration rules after Brexit saw him become an overseas player.

He was a popular player in Somerset's dressing room but has only shown glimpses of his best during two seasons in Taunton. He took 18 wickets as they reached the Blast final in 2021 but has been a peripheral figure this year.

De Lange also impressed in the first season of the Hundred, taking the competition's first five-wicket haul for Trent Rockets last year, but has been kept out of their side by Daniel Sams so far this season.

"De Lange is currently registered as an overseas player but it is anticipated that he will qualify as an English domestic player ahead of the start of next season," Gloucestershire said in a club statement.

The move is a significant boost for Gloucestershire, who have lost three key short-form players in recent weeks, in Benny Howell (to Hampshire), Ryan Higgins (to Middlesex) and Ian Cockbain (released).

"I am very excited to have committed my long term future with the club," de Lange said in a statement. "I really look forward to working with Dale Benkenstein [the head coach] as we have a mutual goal for the future of Gloucestershire.

"I'm eager to get going, it's a fresh start for me at a new club which is very exciting. I want to help Gloucestershire challenge for silverware and I also want to pass on advice and help the young players who are coming through the ranks."

Steve Snell, Gloucestershire's performance director, said, "I feel Marchant will add a point of difference with his extreme pace and career record of taking a high volume of wickets. Marchant will add significant firepower to our squad with the ball, and I believe he will be a figure of positive influence in and around the dressing room."

Andy Hurry, Somerset's director of cricket, said, "Marchant played a big role in us reaching the Vitality Blast Final in 2021. However, first XI opportunities across the formats have been limited for him this summer. Moving forward, we are not in a position to guarantee him first-team cricket and we therefore completely understand his desire to seek competitive opportunities elsewhere."