The Martin 4-0-4 was an American pressurized passenger airliner built by the Glenn L. Martin Company. In addition to airline use initially in the United States, it was used by the United States Coast Guard and United States Navy as the RM-1G (later as the VC-3A).

When production of the earlier Martin 2-0-2 was stopped due to problems with wing structural failure the company decided to re-wing an improved version (which had already flown as the Martin 3-0-3). The new aircraft was the Martin 4-0-4. It had structural changes to the wings, pressurization and was lengthened slightly to take 40 passengers. Like the earlier 2-0-2, the 4-0-4 was a cantilever monoplane with a standard tail unit (cantilever tailplane and single vertical stabilizer). It had an airstair in the lower tail section for passenger boarding and disembarkation, retractable tricycle landing gear and was powered by two Pratt & Whitney R-2800-CB16 radial piston engines.