David Hamilton Koch ( KOHK; May 3, 1940 – August 23, 2019) was an American businessman, political activist, philanthropist, and chemical engineer. In 1970, he joined the family business: Koch Industries, the second largest privately held company in the United States. He became president of the subsidiary Koch Engineering in 1979, and became a co-owner of Koch Industries (along with elder brother Charles) in 1983. Koch served as an executive vice president of Koch Industries until he retired due to health issues in 2018.

Koch was a libertarian. He was the 1980 Libertarian candidate for Vice President of the United States and helped finance the campaign. He founded Citizens for a Sound Economy and donated to advocacy groups and political campaigns, most of which were Republican. Koch became a Republican in 1984; in 2012, he spent over $100 million in a failed bid to oppose the re-election of President Barack Obama.

Koch was the fourth-richest person in the United States in 2012 and was the wealthiest resident of New York City in 2013. As of June 2019, Koch was ranked as the 11th-richest person in the world (tied with his brother Charles), with a fortune of $50.5 billion. Koch contributed to the Lincoln Center, Sloan Kettering, NewYork–Presbyterian Hospital, and the Dinosaur Wing at the American Museum of Natural History. The New York State Theater at Lincoln Center, home of the New York City Ballet, was renamed the David H. Koch Theater in 2008 following Koch's gift of $100 million for the renovation of the theater.