Elizabeth Anne Holmes (born February 3, 1984) is an American biotechnology entrepreneur who was convicted of fraud in connection with her blood-testing company, Theranos. The company's valuation soared after it claimed to have revolutionized blood testing by developing methods that needed only very small volumes of blood, such as from a fingerprick. In 2015, Forbes had named Holmes the youngest and wealthiest self-made female billionaire in the United States on the basis of a $9-billion valuation of her company. In the following year, as revelations of fraud about Theranos's claims began to surface, Forbes revised its estimate of Holmes's net worth to zero, and Fortune named her in its feature article on "The World's 19 Most Disappointing Leaders".

The decline of Theranos began in 2015, when a series of journalistic and regulatory investigations revealed doubts about the company's claims and whether Holmes had misled investors and the government. In 2018, the U.S. Securities and Exchange Commission (SEC) charged Theranos, Holmes, and former Theranos chief operating officer (COO) Ramesh "Sunny" Balwani with raising $700 million from investors through a fraud involving false or exaggerated claims about the accuracy of the company's blood-testing technology; Holmes settled the charges by paying a $500,000 fine, returning 18.9 million shares to the company, relinquishing her voting control of Theranos, and accepting a ten-year ban from serving as an officer or director of a public company.

In June 2018, a federal grand jury indicted Holmes and Balwani on fraud charges. Her trial in the case of U.S. v. Holmes, et al. ended in January 2022 when Holmes was convicted of defrauding investors, and acquitted of defrauding patients. She was sentenced to serve 11+1⁄4 years at Federal Prison Camp, Bryan, beginning on May 30, 2023. She and Balwani were ordered to pay $452 million in restitution to the victims of the fraud. The credibility of Theranos was attributed in part to Holmes's personal connections and ability to recruit the support of influential people, including Henry Kissinger, George Shultz, James Mattis, and Betsy DeVos, all of whom had served or would go on to serve as U.S. presidential cabinet officials.

Holmes was in a clandestine romantic relationship with Balwani throughout most of Theranos's history. Holmes and Balwani jointly ran the company with a "dysfunctional corporate culture" of "secrecy and fear" according to employees. Staff also claimed that those who "raised concerns or objections" were "usually marginalized or fired" by the pair. Following the collapse of Theranos, Holmes started dating hotel heir William "Billy" Evans, whom she married in 2019 and had two children with (born in 2021 and 2023).