When Jeff Bezos founded an online bookseller named Amazon in 1994, he said the question that he was asked most frequently was “What’s the internet?”

Mr. Bezos answered by building Amazon into a $1.7 trillion behemoth that sold so many different items online it became known as “the everything store.” In the process, he upended the retail industry, turned Amazon into a logistics giant, and expanded into cloud computing, streaming entertainment and artificial intelligence-powered devices. For a time, he was the world’s richest person.

On Tuesday, Mr. Bezos, 57, said his run at the top of the Seattle-based company was over.

As Amazon reported its latest set of blockbuster financial results, Mr. Bezos said he planned to hand over the reins this summer and transition into the role of executive chairman. Andy Jassy, 53, the chief executive of Amazon’s cloud computing division, will be promoted to run the entire company. The change will be effective in the third quarter, which starts in July.