Thomas M. Siebel (born November 20, 1952) is an American businessman, technologist, and author. He founded the enterprise software company Siebel Systems and later founded C3.ai, an artificial intelligence software platform and applications company, where he served as CEO for over a decade. As of February 2026, Forbes estimates his net worth at $4 billion.
Siebel has been a prominent figure in the technology industry since the 1980s, transitioning from database management at Oracle to pioneering customer relationship management (CRM) software, and subsequently to enterprise AI solutions. His work has influenced how large organizations manage customer interactions and adopt AI for operational efficiency.
Early Life and Education
Siebel was born in Chicago, one of seven children of Arthur Francis Siebel and Ruth A. (née Schmid) Siebel. He pursued higher education at the University of Illinois, earning a BA in history, an MBA, and an MS in computer science. The university later awarded him an honorary doctorate in engineering, recognizing his contributions to technology and business.
Career at Oracle and Siebel Systems
Siebel began his career at Oracle Corporation in 1984, holding several management positions until 1990. During his tenure, he identified an opportunity to commercialize an internal sales-force automation tool called Oasis (Oracle automated sales information system). In 1989, he proposed this idea to Larry Ellison, who declined, citing no commercial potential. This decision led Siebel to leave Oracle in 1993 and found Siebel Systems.
Siebel Systems focused on customer relationship management (CRM) applications, a market that grew rapidly. By 1999, Deloitte & Touche recognized it as one of the fastest-growing technology companies in the United States. In 2000, Siebel Systems reported over 8,000 employees across 32 countries, more than 4,500 corporate customers, and annual revenue exceeding $2 billion. Oracle acquired Siebel Systems in 2005, and Siebel served as chairman and CEO until the acquisition.
C3.ai and Enterprise AI
In 2009, Siebel founded C3.ai, an enterprise AI software company, and became its CEO in 2011. Under his leadership, C3.ai developed a platform for deploying machine learning applications across industries such as energy, manufacturing, and healthcare. The company went public in 2020, and Siebel remained CEO until 2025, when he transitioned to executive chairman after being diagnosed with an autoimmune disease that caused visual impairment.
In 2019, Siebel initiated a program at C3.ai covering the cost for employees to complete the University of Illinois’s online Master of Computer Science (MCS) degree through Coursera. Employees who complete the degree receive a 15% salary increase, a $25,000 cash bonus, and additional stock options, reflecting his commitment to workforce education.
Philanthropy and Honors
Siebel has been a significant philanthropist, particularly in education. In 2001, he donated $32 million to the University of Illinois for the Siebel Center for Computer Science, which opened in 2004. He later donated $4 million for endowed professorships and pledged $100 million in 2007. In 2016, he funded the Siebel Center for Design, a 60,000-square-foot facility completed in 2020.
He founded the Siebel Scholars Foundation and the Montana Meth Project, and has held advisory roles at Stanford University, the University of California, Berkeley, and Princeton University (as a trustee from 2008 to 2011). Barron's ranked him among the world's top 25 philanthropists in 2009 and 2010, and BusinessWeek included him in its list of The 50 Most Generous Philanthropists in 2007 and 2008.
Political Involvement and Personal Life
In February 2022, Siebel donated $90,000 to the Canada convoy protest in Ottawa, which opposed COVID-19 vaccine mandates. In 2024, he donated $500,000 to Donald Trump’s re-election campaign and organized a fundraiser for the politician. In 2025, he donated $1 million against California's Proposition 50, making him the third-largest single donor opposing the bill.
Siebel lives in Woodside, California, with his wife Stacey and their four children. He is the second cousin of Jennifer Siebel Newsom, the First Partner of California. In 2022, he ranked first among Americans for personal CO2 emissions from private jet use. In early 2025, he was diagnosed with giant cell arteritis, causing significant visual impairment.
In August 2009, while in Tanzania, Siebel survived an elephant attack that broke several ribs, gored his left leg, and crushed his right. After 19 reconstructive surgeries over two and a half years, he fully recovered. His account was featured in National Geographic's TV series Dead or Alive: Trampled on Safari in 2013.
Books and Articles
Siebel has authored several books and articles on technology and business, including Digital Transformation (2019), Taking Care of eBusiness (2001), Cyber Rules (with Pat House, 1999), and Virtual Selling (with Michael Malone, 1996). His articles have appeared in McKinsey Quarterly and Stanford Energy Journal, among others.