William B. Kouwenhoven (1886–1975) was an American electrical engineer and researcher whose work led to the development of the cardiac defibrillator and modern cardiopulmonary resuscitation (CPR), revolutionizing emergency treatment for cardiac arrest.

Tjalling C. Koopmans (1910–1985) was a Dutch-born American economist who won the 1975 Nobel Prize in Economics for work on optimal resource allocation and linear programming, helping establish the field of mathematical economics.

Willem de Kooning (1904–1997) was a Dutch-born American painter and leading figure in Abstract Expressionism. Known for powerful, expressive works such as his Woman series, he became one of the most influential artists of the twentieth century.

Hans Koning (1921–2007), born Hans Koningsberger, was a Dutch-born American novelist, journalist, and screenwriter. A former member of the Dutch resistance during World War II, he later wrote widely for major magazines and newspapers.

Willem J. Kolff (1911–2009) was a Dutch-born physician and biomedical pioneer who invented the first practical artificial kidney and helped develop artificial organs, including early artificial heart technology, saving countless patients suffering from kidney and heart failure.

Harry Koch (1867–1942) was a Dutch immigrant, printer, and newspaper publisher in Quanah, Texas. He founded the Quanah Tribune-Chief and was the father of Fred C. Koch and grandfather of industrialists Charles and David Koch.

William I. Koch (born 1940) is an American businessman and entrepreneur who founded the Oxbow Group after selling his stake in Koch Industries. He is also known for financing the winning 1992 America’s Cup sailing team.

Frederick R. Koch (1932–2020) was an American collector, philanthropist, and eldest son of Koch Industries founder Fred C. Koch. Unlike his brothers, he pursued the arts, building major collections of rare books, manuscripts, and drawings.

Fred C. Koch (1900–1967) was an American chemical engineer and entrepreneur who developed innovative oil refining processes and founded businesses that evolved into Koch Industries, which later became the largest privately held corporation in the United States.

David H. Koch (1940–2019) was an American businessman, philanthropist, and executive vice president of Koch Industries. A co-owner of the company, he became widely known for major charitable donations supporting medical research, education, and cultural institutions.