Sudharsan, 21, made a recent century against Pakistan A, and plays for Tamil Nadu in the Ranji Trophy. He made 96 in this year's Indian Premier League final for Gujarat Titans
Surrey have signed Sai Sudharsan for the County Championship run-in, with the India A batter coming "highly recommended" to Alec Stewart by "a couple of greats of the Indian game".
The Division One leaders are set to be without several players for the final throes of the season, with Ollie Pope injured, Tom Latham and Sean Abbott both having returned home, and Will Jacks, Gus Atkinson and Sam Curran all in England's white-ball squads to face New Zealand.
Sudharsan, 21, made a recent century against Pakistan A, and plays for Tamil Nadu in the Ranji Trophy. He made a fine 96 in this year's Indian Premier League final for Gujarat Titans.
"With the busy schedule of international and domestic cricket around the world, I'm pleased to add Sai Sudharsan to our available squad of players," said Stewart, Surrey's director of cricket. "Sai has come highly recommended to me by people I hugely respect, including a couple of the greats of the Indian game, who have seen and worked closely with him.
Sudharsan comes highly rated to Alec Stewart (Punit Paranjpe/AFP via Getty Images)
"Sai will add to the batting options for the final three games of the season, and we look forward to welcoming him to the dressing room."
Surrey have already re-signed Kemar Roach for September; he began the season at the Kia Oval and replaces Abbott.
Sudharsan arrives in time to feature against Warwickshire on September 3, and he is set to be available for further clashes against Northamptonshire and Hampshire.
Essex, Surrey's nearest title rivals, have bolstered their resources by signing Umesh Yadav, Sudharsan's countryman.
Surrey, meanwhile, have handed new contracts to Josh Blake, Matt Dunn and Jamie Overton.