Joe Gatting has agreed a two-year contract with Hampshire.
The 26-year-old middle-order batsman, whose uncle is former England captain Mike Gatting, will move to the Ageas Bowl after spending the last five seasons with Sussex.
"I am delighted to be joining such a fantastic club, as soon as I heard Hampshire where interested in me it became clear that's where I wanted to play my cricket," said Gatting.
"I've heard and seen nothing but good things. I can't wait for the new chapter and fresh start at Hampshire and I can't wait to get started."
Hampshire Director of Cricket, Giles White said: "We expect to see less and less of Michael Carberry due to international commitments so Joe comes in to add depth to our batting.
"He has shown he is a talented batsman and an athletic fielder and we expect him to be a good addition to the squad as well; we hope he makes strides in fulfilling his potential over the next couple of years."
Gatting, who made 145 appearances for Sussex during his time with the county and averages 29.91 in first-class matches, is the second batsman to join Hampshire since the end of last season, following the capture of Will Smith in October.