Mr. Williams was long considered a leading candidate to replace Tim Cook as the company’s next chief executive.

The legendary Apple design team hasn't had much luck holding onto leadership since Jony Ive left, and with COO Jeff Williams retiring, the leadership role will shift to CEO Tim Cook.

Having worked at Apple for nearly three decades, Williams has played a significant role in introducing the iPod and iPhone programs, leading the development of the Apple Watch, and overseeing the design team,