Tymshare, Inc was a time-sharing service and third-party hardware maintenance company competing with companies such as CompuServe, Service Bureau Corporation and National CSS. Tymshare developed or acquired various technologies, such as data networking, electronic data interchange (EDI), credit card and payment processing, database technology, and more. It was headquartered in Cupertino, California from 1964 to 1984.

In 1984 Tymshare was acquired by Nathan Baker, to which Tymshare had sold its hospital accounting service in 1982. Tymshare was restructured, split up and portions were resold, spun off, and merged with other companies from 1984 through 2004 when most of its legacy network was eventually shut down. Islands of its network technology continued as part of EDI, into 2008.

McDonnell Douglas was acquired by Boeing. Consequently, rights to use technology developed by Tymshare are currently held by Boeing, British Telecom (BT), Verizon Communications, and AT&T Inc. due to the acquisitions and mergers from 1984 through 2005.