Chatham Borough is a suburban borough in Morris County, in the U.S. state of New Jersey. As of the 2020 United States census, the borough's population was 9,212, an increase of 250 from the 2010 census count of 8,962, which in turn reflected an increase of 502 from the 8,460 counted in the 2000 census. The area that is now Chatham has been inhabited by humans for thousands of years.