Background and career
Thomas M. Siebel () is an American businessman, information technologist, and author. He founded the enterprise software company Siebel Systems and is the founder, chairman, and CEO of C3.ai, an artificial intelligence software platform and applications company.
Thomas M. Siebel was born in Chicago, being one of seven children of Arthur Francis Siebel and Ruth A. (née Schmid) Siebel. He graduated from the University of Illinois with a BA in history, an MBA and an MS in computer science.
Siebel was an executive at Oracle Corporation between 1984 and 1990, holding several management positions. He was the CEO of Gain Technology, a multimedia software company that merged with Sybase in December 1992. Siebel later founded Siebel Systems, where he was chairman and CEO before Oracle acquired the company in January 2006. He is the chairman of First Virtual Group, a holding company with participating interests in different sectors of activity.
In 1989, as an executive at Oracle, Siebel proposed turning an internal sales-force automation tool called Oasis (Oracle automated sales information system) into a commercial product, but Larry Ellison declined, claiming to see no commercial potential. In 1993, Siebel left Oracle and founded Siebel Systems, a software company primarily engaged in the design, development, marketing, and support of customer relationship management (CRM) applications. By 1999, Siebel Systems was recognized by Deloitte & Touche as one of the most rapidly expanding technology companies in the United States. In 2000, Siebel reported that Siebel Systems had grown to over 8,000 employees in 32 countries, with more than 4,500 corporate customers and annual revenue exceeding $2 billion. Siebel Systems was acquired by Oracle in 2005.
Siebel founded enterprise artificial intelligence company C3 AI in 2009 and has led the company as CEO since 2011. He transitioned to the role of executive chairman in 2025 after being diagnosed with an autoimmune disease that left him visually impaired. In 2019, Siebel initiated a program at C3 AI that covers the cost for employees to complete the University of Illinois’s online Master of Computer Science (MCS) degree through Coursera. Employees who complete the MCS receive a 15% salary increase, a $25,000 cash bonus, and additional stock options.
As of 3 October 2026, Forbes put Siebel's real-time net worth at $4.6 billion.
Sources
Net-worth figure: Celebrity Net Worth (October 2026), in USD. Biography and career facts: the person's Wikipedia article and linked reporting. Snapshot date for all StarWorth figures: 28 October 2026.
