The fourth season of the American fictional drama television series ER first aired on September 25, 1997, and concluded on May 14, 1998. The fourth season consists of 22 episodes.

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.