Douglas Hanahan (born 1951) is an American biologist, professor and director emeritus of the Swiss Institute for Experimental Cancer Research at EPFL (École polytechnique Fédérale de Lausanne) in Lausanne, Switzerland. He is currently member of the Lausanne branch of the Ludwig Institute.
He received his PhD from Harvard University in 1983. In 1983, he developed Super Optimal Broth, a microbiological growth medium. He also improved the protocols used for plasmid transformation of Escherichia coli. In the 1980s, he developed one of the first transgenic mouse models of cancer. With Robert Weinberg, he wrote a seminal paper The Hallmarks of Cancer, published in January 2000, and which in March 2011 is the most often cited article from the peer reviewed journal Cell. In 2011, they published an updated review article entitled "Hallmarks of cancer: the next generation". In 2022, Professor Hanahan published another updated review article entitled "Hallmarks of Cancer: New Dimensions" on the peer reviewed journal Cancer Discovery.