A.J.F. Van Laer (1869–1955) was a Dutch American archivist and historian who translated and edited early Dutch records of New Netherland and Albany, preserving key seventeenth-century colonial documents despite major losses in the 1911 New York Capitol fire.

Peter Kuyper and his wife Lucille acquired the Rolscreen window screen company in 1925 and moved it to Pella, Iowa. Their firm evolved into the Pella Corporation, a major manufacturer of windows and doors.

Gerard Kuiper (1905–1973) was a Dutch-born astronomer and pioneer of modern planetary science. He discovered several planetary satellites and atmospheres and proposed the Kuiper Belt, a distant region of icy bodies beyond Neptune believed to be the source of many comets.

Louis Kregel (1888–1939) and his son Robert Kregel (1919–2011) were Dutch American booksellers and publishers who built Kregel Books in Grand Rapids, Michigan into a leading distributor and publisher of Christian literature.

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.