The Ether Dome is a surgical operating amphitheater in the Bulfinch Building at Massachusetts General Hospital in Boston. It served as the hospital's operating room from its opening in 1821 until 1867. It was the site of the first public demonstration of the use of inhaled ether as a surgical anesthetic on October 16, 1846, otherwise known as Ether Day. Crawford Long, a surgeon in Georgia, had previously administered sulfuric ether in 1842, but this went unpublished until 1849. The Ether Dome event occurred when William Thomas Green Morton, a local dentist, used ether to anesthetize Edward Gilbert Abbott. John Collins Warren, the first dean of Harvard Medical School, then painlessly removed part of a tumor from Abbott's neck. After Warren had finished, and Abbott regained consciousness, Warren asked the patient how he felt. Reportedly, Abbott said, "Feels as if my neck's been scratched". Warren then turned to his medical audience and uttered "Gentlemen, this is no Humbug". This was presumably a reference to the unsuccessful demonstration of nitrous oxide anesthesia by Horace Wells in the same theater the previous year, which was ended by cries of "Humbug!" after the patient groaned with pain.

William Thomas Green Morton (August 9, 1819 – July 15, 1868) was an American dentist and physician who first publicly demonstrated the use of inhaled ether as a surgical anesthetic in 1846. The promotion of his questionable claim to have been the discoverer of anesthesia became an obsession for the rest of his life.