He died in Los Angeles, his talent company, Creative Artists Agency told Reuters. The Emmy-winning "M*A*S*H" lasted 11 seasons, becoming one of the most honored shows in U.S. television history before ending in 1983, with a final episode that set a record by attracting more than 106 million viewers.

Gelbart penned the 1972 pilot for "M*A*S*H," a comedy set in the 1950s Korean War, which used that conflict as an allegory for the Vietnam War, in which the United States was embroiled during the early years of the series. The show, based on a 1970 movie of the same name by director Robert Altman, was about wise-cracking doctors operating on the wounded just a few miles from the front lines, in what they called "meatball surgery," because it called for quick action.

Producer and director Gene Reynolds called on Gelbart to write the pilot script for "M*A*S*H," and he went on to write for other episodes. He also served as executive script consultant and shared an Emmy award with Reynolds when the series won for outstanding comedy in 1974.