W illiam "Bill" Koch is an American billionaire businessman and a member of the powerful Koch family. He is the fraternal twin brother of David Koch and the younger brother of Charles Koch, who famously control the massive industrial conglomerate, Koch Industries. However, Bill's relationship with his brothers has been famously acrimonious. In the 1980s, he and his other brother, Frederick, launched a hostile but ultimately unsuccessful attempt to take control of the family's company. They were later bought out of their stake in the company for a massive sum.

Since then, Bill Koch has forged his own business path, founding the Oxbow Group, a private holding company with interests primarily in energy and mining, including coal and natural gas. In addition to his business career, he is an avid collector of art and wine, with a world-class collection. He is also a passionate and competitive sailor, who famously founded and funded the winning America's Cup team in 1992.