(Corrects official's title from deputy governor to sub governor)

CAIRO, May 26 (Reuters) - Egypt's central bank sub governor for monetary policy is joining the International Monetary Fund in August, a central bank source told Reuters on Thursday.

Rania al-Mashat will serve as an advisor to the IMF's chief economist, the source said.

"She did not resign from the central bank but she is going on sabbatical," the source told Reuters.

Mashat joined the central bank in August 2005. At the time she was the youngest sub governor for monetary policy in the bank's history.

(Reporting by Ehab Farouk; Writing by Ahmed Aboulenein) ((ahmed.aboulenein@thomsonreuters.com; +20 2 2394 8097; Reuters Messaging: ahmed.aboulenein.thomsonreuters.com@reuters.net))