Ornge (pronounced Orange), formerly Ontario Air Ambulance Corporation and Ontario Air Ambulance Service, is a Canadian not-for-profit corporation and registered charity that provides air ambulance and associated ground transportation services for the province of Ontario, under the direction of the province's Ministry of Health. The provision of ambulance services in Ontario is governed by the Ambulance Act, which states that the Minister of Health "has the duty and the power" to make sure Ontario is serviced by a "balanced and integrated system of ambulance services and communication services used in dispatching ambulances." Its headquarters are in Mississauga, Ontario, Canada.

The name Ornge is not an acronym, but is based on the orange colour of the organization's aircraft and land ambulances. According to the organization, "The 'a' was removed from the name, partly to make people stop and take a second look, and also so that it could be trademarked."

As of 2024, Ornge has the largest air ambulance and critical care land ambulance fleet in Canada, and employs more than 700 people, including paramedics, pilots, and aviation specialists. It serves more than 14 million people over one million square kilometres of land, deploying from 14 bases across Ontario as well as its Mississauga, Ontario, Canada headquarters. Ornge is responsible for approximately 20,000 patient-related transports per year. It also contracts some of its non-urgent patient transport service in Northern Ontario to private air carriers.

Prior to Ornge, the air ambulance program was established in 1977 to serve remote areas, primarily in Northern Ontario, that are inaccessible to land ambulances or that land ambulances would take too long to reach. Ontario was the first Canadian province to provide a helicopter-based air ambulance system to transport critically ill patients to hospital. Air ambulances are also used to transport medical teams and organs for transplant. A large part of the air ambulance service is involved in serving aboriginal communities, of which there are approximately 117, in 6 treaty areas of Northern Ontario.

The first air ambulance, "Bandage One" a Bell 212, was operated out of Buttonville Airport by private operator Viking Helicopters Incorporated (later to become part of Canadian Helicopters). A second Bell 212, "Bandage Two", was after one year pilot deemed successful and located in Sudbury, Ontario, followed by "Bandage Three" in Thunder Bay, "Bandage Four" in Timmins and "Bandage Five" in Sioux Lookout for a total of 5 by 1981. Fixed-wing service began in 1978, provided by Austin Airways, with a Timmins based Cessna Citation I. Eventually almost 90 private aircraft would be employed.

This arrangement lasted more than 25 years, until about 2005, as the Ministry of Health and Long-Term Care contracted with private operators to provide its air ambulance program's aircraft, pilots and paramedics. The Ministry directly operated the central air ambulance dispatch centre and was responsible for overseeing the overall effectiveness of the air ambulance program.

In 2005, the Ministry announced that it was appointing a not-for-profit corporation called the Ontario Air Ambulance Corporation to be responsible for all air ambulance operations. This was done to establish clearer lines of authority among the different parts of air ambulance operations. An arm's-length corporation was also consistent with the Ministry's objective of moving away from direct service delivery. The corporation's name was subsequently changed to Ornge. Ornge was described in 2012 as being neither a Crown corporation nor an agency directly controlled by the Government of Ontario, but rather a non-profit organisation incorporated under the federal Canada Corporations Act.

The Ministry operated an air ambulance dispatch centre in Toronto until Ornge took over and MATC (Medical Air Transport Centre) became the Ornge Communications Centre.