The 4077 Mobile Army Surgical Hospital (MASH) is a U.S. Army field hospital located near Ouijongbu. Major areas of the hospital compound include the mess tent, the Officers' Club, the Swamp, the latrine, the hospital tent (which includes the Pre-op Ward, the O.R., and the Post-op Ward), the various nurses' and enlisted tents, the Commander's tent, the V.I.P. tent, the Helicopter pad, and Margaret's tent.
- Lt. Col. Henry Braymore Blake (novels, movie, TV series)
- Col. Sherman T. Potter (TV series only)
- Maj. Frank Burns (in the absence of Lt. Col. Blake or Col. Potter) (appeared in novels, movie, and TV series, but only assumed command in TV series)
- Maj. Charles Emerson Winchester, III (in the absence of Col. Potter after replacing Burns) (TV series only)
- Capt. Benjamin Franklin "Hawkeye" Pierce(as Chief Surgeon, during the absence of Col. Potter, while Maj. Winchester was ill or too involved in a case) (TV Series only)