American entrepreneur who cofounded America Online, Inc. (AOL) (AOL), the world's foremost Internet service provider (ISP), and negotiated the merger in 2001 of AOL and Time Warner Inc. to create a global media and entertainment conglomerate.

From a young age Case and his brother Dan—later a millionaire venture capitalist—devised business opportunities for themselves. After graduating (1981) from Williams College with a degree in political science, Case held positions in the marketing departments of Procter & Gamble, Pizza Hut, Inc., and Control Video Corp., a start-up company that intended to offer consumers downloadable video-game software via telephone lines. The plan failed, but the company—at Case's suggestion—regrouped and, under the name Quantum Computer Services (QCS), began providing an online network for users of Commodore 64 computers. QCS, employing a user-friendly graphical interface originally developed by Apple Computer, Inc. (now Apple Inc.), became America Online, Inc., in 1991 and steadily outpaced all other online services in number of subscribers.

By 2000 Case had built AOL into the world's largest ISP and engineered AOL's takeover of rival CompuServe and of the World Wide Web-browser company Netscape Communications. He had also arranged deals that would ensure delivery of AOL services via satellite television, palmtop computers, and wireless telephones. In late 1999 he initiated talks with media and entertainment company Time Warner that in 2001 resulted in the largest merger in corporate history up to that time and signaled the coming of age of the dot-com industry of Internet-related businesses. Case became chairman of the board of the newly created AOL Time Warner Inc., but in 2002 the enterprise reported a record quarterly loss for a U.S. company, $54.24 billion. In 2003 the conglomerate reverted to the name Time Warner Inc., and Case resigned as chairman.