Apple said Monday afternoon that Tim Cook will step down as CEO, a role he has held since 2011, when he succeeded the late Steve Jobs. Senior Vice President of Hardware Engineering John Ternus will take the top executive position on September 1 of this year.

Cook will remain at the company as executive chairman, and Ternus will join Apple’s board of directors. Arthur Levinson, who has served as Apple’s non-executive chairman for the past 15 years, will become lead independent director, also effective September 1.

The transition has been expected for some time and ends one of the longer and more impactful runs a CEO has had at any company. Cook took the reins at a moment of true uncertainty — Jobs died of pancreatic cancer just six weeks after formally handing off the job — and inherited a company that many industry watchers and enthusiasts struggled to separate from its famed founder. What he leaves behind is a $4 trillion business with annual revenue that has more than quadrupled on his watch.

“It has been the greatest privilege of my life to be the CEO of Apple,” Cook said in a statement on Monday. “I love Apple with all of my being, and I am so grateful to have had the opportunity to work with a team of such ingenious, innovative, creative, and deeply caring people who have been unwavering in their dedication to enriching the lives of our customers.”

When Cook arrived in Cupertino in 1998, he wasn’t hired to be a visionary. Instead, Jobs, who’d recently returned to Apple after years away, needed someone to fix a supply chain that was, by most accounts, a disaster. Cook, a native of Mobile, Alabama, who spent 12 years at IBM before stints at Intelligent Electronics and Compaq, did what was needed and more. He quickly closed warehouses and consolidated suppliers, and he’s been widely credited with turning Apple’s manufacturing operation into a competitive advantage over time instead of a liability.

His promotion to CEO was never a foregone conclusion.

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