Born in Hyderabad, India in 1967, Nadella received a bachelor's degree in electrical engineering from Mangalore University, a master's degree in computer science from the University of Wisconsin, Milwaukee, and a master's of business administration from the University of Chicago.
He joined Microsoft in 1992 after being a member of the technology staff at Sun Microsystems.
One of his first tasks will be integrating Nokia's money-losing handset and services business. Microsoft agreed in September to buy that and various phone patent rights for 5.4 billion euros ($7.2 billion) in one of Ballmer's last major acts as CEO. That deal is expected to be completed by the end of March.