David Hamilton Koch was an American billionaire industrialist, businessman, philanthropist, and political activist, best known as one of the Koch brothers who co-owned and expanded Koch Industries into one of the largest privately held companies in the United States. He served as co-CEO and executive vice president, overseeing diversification into refining, chemicals, and commodities, contributing to the company's annual revenues exceeding $100 billion by the time of his retirement in 2018. Born on May 3, 1940, in Wichita, Kansas, to Fred C. Koch, a chemical engineer and founder of the family business, and Mary Robinson Koch, David grew up in a family deeply involved in engineering and conservative politics. He earned bachelor's and master's degrees in chemical engineering from the Massachusetts Institute of Technology (MIT) in 1962 and 1963, respectively. Politically, Koch was a major donor and funder to libertarian and conservative causes and organizations through both personal and corporate channels, running as the Libertarian Party's vice presidential candidate in 1980 alongside Ed Clark, and later influencing Republican politics through a vast network of organizations that spent nearly a billion dollars on conservative advocacy at its peak. His philanthropic efforts, channeled through the David H. Koch Charitable Foundation, included over $1 billion in lifetime donations, with significant portions supporting medical research (particularly cancer initiatives at institutions like Memorial Sloan Kettering Cancer Center, including a $150 million gift in 2015), his alma mater MIT, and conservative and libertarian initiatives. He and his brother Charles became symbols of conservative megadonors, often criticized by Democrats for shaping policy on issues like climate change and taxation, though Koch himself emphasized free-market principles and individual liberty. Married to Julia Flesher since 1996, he had three children and resided primarily in New York City. Koch battled prostate cancer for over a decade before his death on August 23, 2019, in Southampton, New York, at age 79, leaving a net worth estimated at $58 billion, inherited by his widow.