The founder of apparel retailer Gap Inc, Donald Fisher, is to step down as chairman of the company in May next year.

Fisher, 75, will be replaced by his 49-year-old son Robert, a former Gap executive, but will continue to serve on the board and as an advisor to CEO Paul Pressler.

"It's time for a change because we really are breaking a lot of new ground right now," the outgoing chairman said.

"We have a new CEO and I am totally ecstatic about the way the company is going.

"I will remain as active in the company as they want me to be."

Fisher founded Gap in 1969 with a single San Francisco store, selling specially-fitted jeans and records.

Today, the company has grown to operate more than 3000 retail outlets worldwide, encompass the Banana Republic and Old Navy chains, and produce annual sales of about $15 billion.

Robert Fisher, who holds a six per cent stake in Gap worth about $1.1bn, served as division president of both Banana Republic and Gap, CFO and even store manager during his 19 years with the company.