Australia off-spinner Nathan Lyon will join Hampshire as an overseas player for the 2020 season.
The 31-year-old will play on a red-ball only contract in the County Championship and should be available for April's early-season fixtures.
"We're absolutely delighted with his signature and can't wait to have him on board," Hampshire director of cricket Giles White told BBC Radio Solent.
"He's got a real appetite to play county cricket and to be here."
Lyon took 20 wickets during the drawn Ashes Test series last summer to help his country retain the urn.
He previously played county cricket for Worcestershire in 2017.
"If you look at our bowling attack at the moment, the gap has maybe been taking wickets with spinners," said White.
"With a new groundsman in Simon Lee also joining the club, having worked at Somerset, it all seemed to fit to bring in a high-class spinner for red-ball cricket too.
"Nathan's addition makes for a well-balanced attack. In order to win County Championships, which we want to do, we need to take 20 wickets regularly."
Lyon told the club website: "It is a fabulous opportunity to be involved with a leading county who have had a long and successful relationship with Australian cricketers."