Samuel Harris Gibstine Altman (born April 22, 1985) is an American entrepreneur, investor, and chief executive officer of OpenAI since 2019. He is considered one of the leading figures of the AI boom.

Altman dropped out of Stanford University after two years and founded Loopt, a mobile social networking service, raising more than $30 million in venture capital. In 2011, Altman joined Y Combinator, a startup accelerator, and was its president from 2014 to 2019. In 2019, he became CEO of OpenAI and oversaw the successful launch of ChatGPT in 2022. He was ousted from the role by the company's board in 2023 due to a lack of confidence in his leadership, but was reinstated five days later following significant backlash from employees and investors, after which a new board was formed. He has served as chairman of clean energy companies Helion Energy and Oklo (until April 2025). As of July 2025, Altman's net worth is estimated at US$1.8 billion.

Altman was born on April 22, 1985, in Chicago, Illinois, into a Jewish family, and grew up in St. Louis, Missouri. His mother was a dermatologist, and his father a real estate broker. Altman is the eldest of four siblings. At the age of eight, he received his first computer, an Apple Macintosh, and began to learn how to code and take apart computer hardware. He attended John Burroughs School, a private school in Ladue, Missouri. In 2005, after studying computer science for two years at Stanford University, he dropped out without earning a bachelor's degree.

In 2005, at the age of 19, Altman co-founded Loopt, a location-based social networking mobile application. As CEO, he raised more than US$30 million in venture capital for the company, including an initial investment of US$5 million from Patrick Chung of Xfund and his team at New Enterprise Associates, followed by investments from Sequoia Capital and Y Combinator. In March 2012, after Loopt failed to gain significant user traction, the company was acquired by the Green Dot Corporation for $43.4 million.

In 2011, Altman became a partner at startup accelerator Y Combinator (YC), initially working on a part-time basis. In February 2014, he became president of YC. Altman aimed to expand YC to fund 1,000 new companies per year and sought to broaden the types of companies funded, particularly focusing on "hard technology" startups.

In October 2015, Altman was involved in expanding YC's scope. He contributed $10 million to the initial fund of Y Combinator Research, and announced YC Continuity, a fund to invest in maturing YC companies. In September 2016, Altman's role at YC expanded to president of YC Group, which included Y Combinator and other units.

In March 2019, YC announced Altman's transition from president to a less hands-on role as chairman of the board, allowing him to focus on OpenAI. This decision came shortly after YC announced it would be moving its headquarters to San Francisco. As of early 2020, he is no longer affiliated with YC. It was later revealed that he had falsely claimed the board chair title (including in SEC filings), and that Y Combinator partners never approved his appointment.

As of June 2024, Altman's investment portfolio includes stakes in over 400 companies, valued at around US$2.8 billion. Some of these investments intersect with companies doing business with OpenAI, which has raised questions about potential conflicts of interest. OpenAI's chairman of the board, Bret Taylor, maintained that Altman has been transparent about his investments.