SEATTLE — Four senior Microsoft executives, including Stephen Elop and Mark Penn, will leave the technology company in the biggest organizational shake-up yet under Satya Nadella, its chief executive.

In an email sent to Microsoft employees on Wednesday morning, Mr. Nadella said that three of the departures were related to his decision to organize the company’s engineering efforts into fewer groups. The three executives leaving as a result are Mr. Elop, former chief executive of Nokia, who has been leading Microsoft’s devices group; Eric Rudder, leader of its advanced technology and education efforts; and Kirill Tatarinov, head of its business solutions group.

“To better align our capabilities and, ultimately, deliver better products and services our customers love at a more rapid pace, I have decided to organize our engineering effort into three groups that work together to deliver on our strategy and ambitions,” Mr. Nadella said in the email.

The organizational changes are the most sweeping since Mr. Nadella was named chief executive of Microsoft in February 2014. While Microsoft has a long history of bureaucratic reshufflings, they do not typically involve the departure of so many executives at once.