Surrey head coach Graham Ford is leaving the county to return to the Sri Lanka national team.
The 55-year-old South African left his role as Sri Lanka coach in 2014 to take charge at The Oval.
In 2015, he led Surrey to promotion from County Championship Division Two and to the final of the One-Day Cup, where they lost to Gloucestershire.
"He has played an integral role in the progress that we have achieved," said director of cricket Alec Stewart.
"He has worked tirelessly with the players and his efforts can be seen in their individual performances and the team's results, culminating in promotion back to the First Division.
"It was a very tough decision for Graham to leave Surrey but we understand that the opportunity to go back and coach at international level with Sri Lanka was too good to turn down.
"Despite the timing of his decision, we wish Graham all the best and we will immediately start our search for a new head coach."
Ford, who has also worked for Kent and South Africa, was shortlisted for the England coach's job in 2009, with that role eventually going to Andy Flower.