What is the name of Warren Buffett's mentor at Columbia University?

Warren Buffett’s mentor at Columbia University was Benjamin Graham.

Buffett studied under Graham at Columbia Business School after moving there to learn from the investor whose classes and writings had shaped modern value investing. Graham emphasized buying securities for less than their underlying worth, while demanding a “margin of safety” against error and bad luck.

Graham co-authored Security Analysis with David Dodd and later wrote The Intelligent Investor. Buffett credited Graham’s ideas with transforming his approach to stocks, although Buffett eventually developed a broader preference for buying excellent businesses at reasonable prices. Graham also became Buffett’s employer at Graham-Newman Corporation after Buffett graduated.

A common mix-up is David Dodd, Graham’s Columbia colleague and co-author. Dodd was an important pioneer of value investing, but Graham was the professor Buffett specifically identified as his mentor.