Air-sea rescue (ASR or A/SR, also known as sea-air rescue), and aeronautical and maritime search and rescue (AMSAR) by the ICAO and IMO, is the coordinated search and rescue (SAR) of the survivors of emergency water landings as well as people who have survived the loss of their seagoing vessel. ASR can involve a wide variety of resources including seaplanes, helicopters, submarines, rescue boats and ships. Specialized equipment and techniques have been developed. Both military and civilian units can perform air-sea rescue. Its principles are laid out in the International Aeronautical and Maritime Search and Rescue Manual. The International Convention on Maritime Search and Rescue is the legal framework that applies to international air-sea rescue.

Air-sea rescue operations carried out during times of conflict have been credited with saving valuable trained and experienced airmen. Moreover, the knowledge that such operations are being carried out greatly enhanced the morale of the combat aircrew faced not only with the expected hostile reaction of the enemy but with the possible danger of aircraft malfunction during long overwater flights. As such, many militaries have opted to develop a capable air-sea rescue component, and ensure that such assets are available during most deployments. Early air-sea rescue operations were performed by flying boats or floatplanes, with the first dedicated unit operating such aircraft being established near the final months of World War I. While initially restricted to in-shore operations and with limited equipment, capabilities and resources would be expanded over the following decades. By the start of World War II, various nations were operating capable air-sea rescue units that operated a combination of amphibious and land-based fixed wing aircraft.

Amid World War II, a major innovation was introduced in the form of the helicopter, which provided hover capabilities that were revolutionary for air-sea rescue. The first military helicopter air-sea rescue, by a Sikorsky S-51, occurred in 1946. Over the following decades, more capable rotorcraft, such as the Sikorsky SH-3 Sea King and Eurocopter HH-65 Dolphin, made longer range operations possible, with parallel advances in equipment improving both the speed and the level of help that air-sea rescue platforms could provide. The 1980s additionally saw the formal introduction of training programs for the deployment of rescue swimmers, who have proved invaluable for recovering incapacitated personnel from the sea.

Air-sea rescue operations have been prominent in several major conflicts, such as the Korean War, Vietnam War, and Falklands War. By the start of the twenty-first century, numerous civilian organizations have involved themselves in providing air-sea rescue services, in some circumstances taking over this function from incumbent military operators.

Initial air-sea rescue operations were performed either by flying boats or floatplanes; these were the pioneering approach used to pick up aviators or sailors who were has come into difficulties in the water. Any other aircraft design posed the additional danger of ditching in the water and requiring immediate rescue, while seaplanes could land on the water in an emergency and wait for rescue. Qualities such as their long range, endurance, and the ability to stay on station for long periods of time were commonly viewed as essential naval aviation requirements for rescue aircraft. Robust radio equipment was necessary for contact with land and ocean surface forces.

Training and weather accidents could require an aircrew to be rescued, and seaplanes were occasionally used for that purpose. The limitation was that if the water's surface were too rough, the aircraft would not be able to land. The most that could be done was to drop emergency supplies to the survivors, or to signal surface ships or rescue boats to guide them to the correct location.

The first attempts at an airplane rescuing a downed flyer at sea took place in August 1911, during the 1911 Chicago International Aviation Meet, when, in separate incidents, aviators St. Croix Johnstone and René Simon crashed into Lake Michigan. In both cases, pilot Hugh Robinson, in a Curtiss hydroplane, went out to try to rescue them, but in the case of Johnstone it was too late as the flyer had already drowned. In contrast, Simon's plane had stayed afloat with Simon on top of it; Robinson spotted him and offered to pick him up and fly him back to shore. But Simon, who was comfortable and smoking a cigarette, preferred to wait for a boat to come and tow both him and his plane back to dry land, which is what happened. As per one account at the time, this decision "wrestled from Simon and Robinson the distinction of being the first rescued and rescuer in an airship life-saving feat." Nonetheless, Robinson's role has been termed by one book as "the first airplane rescue at sea by another airplane". Still other books have implied or stated that Robinson did in fact pick up Simon, but this does not align with contemporary accounts.

Dedicated air-sea rescue units were not organized by any nation until the end of World War I. Some rescues were performed, however, by individuals and groups acting on their own initiative, such as the United States Navy Reserve pilot Ensign Charles Hammann who, during the Adriatic Campaign, rescued a fellow aviator adrift in the Adriatic Sea by landing on the water in his seaplane.