Orange County is a county located in the U.S. state of North Carolina. As of the 2010 census, the population was 133,801. Its county seat is Hillsborough. Orange County is included in the Durham-Chapel Hill, NC Metropolitan Statistical Area, which is also included in the Raleigh-Durham-Chapel Hill, NC Combined Statistical Area, which had a 2012 estimated population of 1,998,808. It is home to the University of North Carolina at Chapel Hill, the flagship institution of the University of North Carolina System and the oldest state-supported university in the United States.. where is Orange County