"I'm looking forward to welcoming Tom to The Kia Oval," Surrey's director of cricket, Alec Stewart, said. "He is an international cricketer with a wealth of experience who will add to the quality of our batting line up at a time when we are highly likely to lose players to England for the Ashes.
"As we look to build on the success of 2022, it is important we can bring in quality talent when we need it. I'm confident Tom will be an outstanding addition to the squad of players we already have in place."
Latham has scored more than 10,000 runs in first-class cricket and currently averages 44.19 in the format.
Latham said: ""I'm thrilled to join Surrey this summer. I've really enjoyed my past experiences playing county cricket and the challenge that English conditions bring.
"Surrey has a rich history and having the opportunity to play at one of the world's best cricket venues in The Oval is something I'm relishing. I'm looking forward to joining Rory [Burns], Gareth [Batty] and the team and doing as much as I can to help them successfully defend the Championship this year."