ER is an American medical drama television series created by novelist and physician 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 (a fictionalized version of the real Cook County Hospital) in Chicago, Illinois, and various critical issues faced by the department's physicians and staff.

The show is the second longest-running primetime medical drama in American television history behind Grey's Anatomy, and the seventh longest medical drama across the globe (behind the United Kingdom's Casualty and Holby City, Grey's Anatomy, Germany's In aller Freundschaft, Poland's Na dobre i na złe, and New Zealand's Shortland Street). It won 23 Primetime Emmy Awards, including the 1996 Outstanding Drama Series award, and received 124 Emmy nominations. ER won 116 awards in total, including the Peabody Award, while the cast earned four Screen Actors Guild Awards for Outstanding Ensemble Performance in a Drama Series. As of 2014, ER has grossed over $3 billion in television revenue.