Holden G. Karnofsky, born in 1980 or 1981, is an American nonprofit executive. He graduated from Harvard University with a degree in social studies in 2003, having previously attended Stevenson High School. After his graduation, Karnofsky worked at Bridgewater Associates, an investment management fund. While at Bridgewater, he met Elie Hassenfeld, with whom he would later co-found GiveWell.
In 2007, Karnofsky co-founded GiveWell, a charity evaluator, with Elie Hassenfeld.