Bill Greehey is chairman of NuStar Energy L.P. and the founding chairman and CEO of Valero Energy Corporation. He led the company from its inception in 1980 until he retired as CEO in 2006 and as chair in 2007, when NuStar spun off from Valero. The Harvard Business Review named Greehey one of the world's best performing CEOs based based on his tenure at Valero. A noted philanthropist, he has given over $300 million to charitable causes. He is the founding chairman of Haven for Hope, a national model for transforming the lives of the homeless.