Louis Gerstner will retire as chairman of The Carlyle Group at the end of next month, the firm said yesterday.

Gerstner joined the Washington, D.C.-based private equity giant five years ago after nearly a decade at the helm of IBM. He also served as CEO of RJR Nabisco and as a top executive at American Express.

“Initially, I committed to be chairman of Carlyle for one year,” the 66-year-old Gerstner said. “But year after year I continued to be impressed with Carlyle’s value creation model and its efforts to globalize the firm. However, at this point in my life, I have a number of goals and interests yet to fulfill, requiring me to step back at Carlyle.”

Gerstner will remain a senior adviser to Carlyle’s buyout funds.

The firm did not name a successor to take over when Gerstner steps down on Sept. 30.