Tim Cook is stepping down as Apple CEO effective September 1, 2026, after leading the company for nearly 15 years. He'll be replaced by John Ternus, Apple's head of hardware engineering, while Cook moves into the role of executive chairman. This is one of the most significant leadership transitions in tech, ending Cook's tenure that transformed Apple into a $4 trillion company. Ternus takes over a company facing challenges in iPhone growth and emerging competition in AI, with investors already watching closely for signals about his strategic direction.