Carol Hathaway is a fictional character from the NBC medical drama series ER, portrayed by actress Julianna Margulies. She is the nurse manager in the ER. She regularly appeared throughout the series from the pilot episode to her penultimate episode of the show's sixth season. She was mentioned throughout the series and made her final appearance in season fifteen, the show's last season, when she is revealed to have a new career as a transplant coordinator.

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.