Mary Wittenberg, the race director of the New York City Marathon since 2005 and president and chief executive of the New York Road Runners, is leaving the organization to head Virgin Sport, a new endeavor by the billionaire entrepreneur Richard Branson.
Ms. Wittenberg, 52, led the Road Runners in a period of sharp growth, becoming one of the most powerful female executives in sports. A nonprofit organization, the Road Runners has annual revenue of more than $70 million, half of it earned by the New York City Marathon, the largest marathon in the world with more than 50,000 runners each fall.