The Martin PBM Mariner was a successful US Navy flying boat built to complement the popular PBY Catalina and which served during World War II as well as the post-war era. It featured a gull wing, retractable outrigger floats and a dihedral tailplane with inward-canted twin fins, perhaps its most recognizable feature. The Mariner saw action mostly in the Pacific theater in a variety of roles such as as maritime patrol, anti-submarine warfare (ASW), air-sea rescue, and as a transport capable of carrying up to 20 passengers; it was also exported to Australia and Britain although only being used in service by the former during the Pacific island-hopping campaign, particularly around New Guinea. Radar-equipped Mariners continued in service after the war with the USN and USCG, remaining in production until as late as 1949 with additional service by the Netherlands for use in the Dutch East Indies.

The prototype XPBM-1 was first flown on 18 February 1939 and had been preceeded by a quarter-scale proof of concept aircraft. Deliveries began the following year as the PBM-1 and immediately followed by the PBM-3, the first major production version. Subvariants included the PBM-3B with more powerful engines, the -3C with armor protection, the -3D with radar and self-sealing fuel tanks, the -3R unarmed transport, and the -3S ASW aircraft. Later improvements led to the PBM-5 which entered service during the final phase of the war and with various conversions including the PBM-5A amphibian with retractable undercarriage, the -5E with different radar, the -5G for the US Coast Guard, and the -5S for ASW duties. British units were designated Mariner GR.I but were not used in action.