William David Cohan (born February 20, 1960) is an American business writer. He has written three books about business and economics and is a contributing editor at Vanity Fair.

Prior to becoming a journalist, he worked on Wall Street for seventeen years. He spent six years at Lazard Frères in New York, then Merrill Lynch & Co., and later became a managing director at JP Morgan Chase. He also worked for two years at GE Capital. Cohan is a graduate of Duke University, Columbia University School of Journalism, and Columbia University Graduate School of Business.

Cohan was born in Worcester, Massachusetts on February 20, 1960. His father was an accountant and his mother worked in administration.

In 1991 he married editor Deborah Gail Futter in a Jewish ceremony.

In 2007, he published , about Lazard Frères. It won the 2007 Financial Times and Goldman Sachs Business Book of the Year Award.

His book , describing the last days of Bear Stearns & Co., was published in March 2009. The book has received excellent reviews and was described as a masterfully reported account by Tim Rutten in The Los Angeles Times. It remained on the New York Times Bestseller list for several months.

In an op-ed article in the New York Times, Cohan said in March 2009 that Bear Stearns CEO Alan Schwartz and Lehman CEO Dick Fuld had engaged in a tsunami of excuses when they were responsible for their firms collapse. In another op-ed written with Sandy B. Lewis in June 2009 he said that the current economic crisis is not over yet, and that many of the fixes that the Obama administration has proposed will do little to address them and may make them worse.

His 2011 book, , examines the historical role and influence of Goldman Sachs.

His new book, , about the story of the Duke lacrosse case, was published in 2014 by Scribner.