Apple Inc. is entering a leadership transition that will end one of the most successful executive tenures in modern corporate history, with Chief Executive Tim Cook set to step down after nearly 15 years at the helm and hand over the role to John Ternus.

Cook will move into the position of executive chairman in September, marking a shift rather than a full departure as the company navigates a more complex global and technological landscape. Ternus, currently head of hardware engineering, will assume leadership as the company’s next chief executive.

The transition comes at a time when Apple remains one of the world’s most valuable and profitable companies, largely driven by the enduring strength of the iPhone and a growing services business. During Cook’s tenure, annual profit rose to over $110 billion, while the company’s valuation expanded to roughly $4 trillion.

Cook took over leadership in 2011 following the death of co-founder Steve Jobs, stepping into a role widely regarded as one of the most challenging in the corporate world. He was credited with strengthening Apple’s global supply chain, expanding its international footprint, and building a steady, highly efficient operating model.

“He stepped into the world’s biggest shoes — the biggest shoes that anybody on the planet has ever had to step into — and he’s done an amazing job,” said Peter Oppenheimer, Apple’s former chief financial officer.

Under Cook, Apple broadened its product ecosystem with devices such as the Apple Watch and AirPods, while also accelerating growth in services including digital payments and cloud offerings. These segments now account for a significant share of the company’s revenue.

However, the leadership change comes as Apple faces new pressures. The company has yet to introduce a breakthrough product in recent years and is under increasing scrutiny over its position in artificial intelligence, where competitors have committed massive investments. It is also dealing with geopolitical tensions, regulatory challenges, and shifting trade policies that affect its global supply chain, particularly its reliance on China.

Ternus has spent more than two decades at Apple and played a key role in the development of its Mac and iPad lines. His appointment signals a focus on product engineering as the company looks to define its next phase of growth.

“I am filled with optimism about what we can achieve in the years to come,” Ternus said. “I promise to lead with the values and vision that have come to define this special place for half a century.”

Apple said Cook will continue to support the company in his new role, particularly in engaging with policymakers and managing external relations.

“This is not goodbye,” Cook said in a message, describing the move as a “moment of transition.”

The leadership shift places Ternus at the center of a key question facing the company: how to sustain innovation and remain competitive in a rapidly evolving technology sector while maintaining the scale and stability built over the past decade.