CSA made the announcement today.
The former batsman led South Africa to the top of the test rankings after his appointment on a two-year contract in August 2011.
CSA says Kirsten informed the board he'll be leaving and cited "family reasons" for his decision.
Kirsten has a young family and has often taken time out from his cricket duties to be with his wife and children. He coached India to the World Cup title in 2011 before returning to his home country.