Afghanistan leg-spinner Qais Ahmad will join Gloucestershire in 2020.
The 19-year-old will be available for the club's T20 Blast campaign and the final six County Championship matches of the season.
Ahmad has played one Test match, against Bangladesh in September, and has also appeared for the Hobart Hurricanes in Australia's Big Bash.
He was recently picked by Welsh Fire in the draft for The Hundred, which begins in England next summer.
"We had a very strong season in 2019 and Qais will help take us to the next level in both the long and short formats with his game-changing skills," said Gloucestershire head coach Richard Dawson.
"He's one of the most exciting young spinners in the world and I'm looking forward to seeing him add a new dimension to our T20 and County Championship squads."
Gloucestershire will play in Division One of the Championship next season for the first time since 2005 after securing promotion this summer.
"Having played T20 cricket around the world I have always wanted to play first-class cricket in England to develop my red ball skills. I am looking forward to working with Richard Dawson," Qais said.