John Truman Carter III, M.D. is a fictional character from the NBC television series ER. He was portrayed by Noah Wyle and appeared as one of the series' principal characters from the pilot episode until the eleventh-season finale. Carter's career path is one of the main story arcs of the series, beginning as a third-year medical student, becoming a resident, first in surgery and then in emergency medicine, before being promoted to an attending physician.

ER is an American medical drama television series created by Michael Crichton that aired on NBC from September 19, 1994, to April 2, 2009, with a total of 331 episodes spanning 15 seasons. It was produced by Constant c Productions and Amblin Television, in association with Warner Bros. Television. ER follows the inner life of the emergency room (ER) of Cook County General Hospital in Chicago, and various critical issues faced by the department's physicians and staff.