The Lockheed P-3 Orion remains as one of the premier maritime patrol aircraft in service anywhere in the world despite its 50 years of service in which it was one of the cornerstones of the US's anti-submarine forces during the Cold War. It was developed as a replacement for the P-2 Neptune (in Greek mythology Orion was Neptune's son) and its large size was a requirement for the incorporation of an extensive array of detection systems including a tail-mounted magnetic anomaly detector (MAD) boom as well as the ability to carry a combination of mines, depth bombs, torpedoes, sonobuoys, and more recently, anti-ship missiles like the Harpoon. As such, the P-3 is a fearsome weapon, capable of detecting and destroying both submerged and surface vessels in addition to serving as a battlefield surveillance platform for ground troops such as the Marine Corps as well as an electronic intelligence aircraft, reconnaissance, and even as transports. Some have also been adapted as anti-narcotics and weather platforms. It has also found great success with over a dozen foreign operators most notably Australia, Canada, Germany, Korea, New Zealand and Japan (license-built by Kawasaki). Although P-3s have not been used in combat against submarines, they have undertaken patrol and reconnaissance duties from the Cuban Missile Crisis onwards, including Vietnam, the Gulf War, and the wars in Iraq and Afghanistan, in the later case operating over land. Despite its capabilities, airframe issues have resulted in numerous countries seeking replacements, these include the US with the P-8 Poseidon as well as Japan with the P-1. However, P-3s are still expected to remain in front line service well into the next decade.

First flight of the prototype YP3V-1 was one 25 November 1959 and entered service three years later with the new designation P-3A. Eventually it was decided to incorporate a more poweful enigne and provide the ability to carry the AGM-12 Bullpup anti-ship missile, thus leading to the P-3B. The next major variant was the P-3C which entered service at the end of the decade and which adopted a new set of sensors and technological updates which were further refined over the course of its production run. Export versions of the P-3B include the P-3K (New Zealand), P-3P (Australia), P-3N (Spain) while those based on the P-3C were the P-3W (Australia) and the P-3F for Iran which is the only version of the Orion to be equiped for inflight-refuelling. Canadian versions are known as the CP-140 Aurora with the avionics and electronics suite of the more advanced S-3. Aside from maritime patrol, the P-3 has been extensively refitted for Elint duties, initially as the EP-3A which lacked the MAD boom and later as the EP-3B and E which which feature prominent antenna domes over and under the fuselage. Other roles include the RP-3A and D research aircraft, the WC-3A and D weather reconnaissance variants, the CP-3A transport and the VP-3A executive transport. Lastly, an AWACS version using the same radar as the E-2 is known as the P-3 AEW & C, a few of which have been ordered by the USCG for anti-drug missions.