A flag carrier is a transportation company, such as an airline or shipping company, that, being locally registered in a given state, enjoys preferential rights or privileges, accorded by the government, for international operations. It may be a state-run, state-owned or private but state-designated company or organization. Flag carriers may be known as such due to maritime law requiring all aircraft or ships to display the state flag of the country of their registry.

A flag carrier (if it is a certificated airline rather than a holding company, conglomerate, or multinational private equity firm) may also be known as a national airline or a national carrier, although this can have different legal meanings in some countries.

The term "flag carrier" is a legacy of the time when countries established state-owned airline companies. Governments then took the lead due to the high capital costs of establishing and running airlines. The heavily regulated aviation industry also meant aviation rights are often negotiated between governments, denying airlines the right to an open market. These Bilateral Air Transport Agreements similar to the Bermuda I and Bermuda II agreements specify rights awardable only to locally registered airlines, forcing some governments to jump-start airlines to avoid being disadvantaged in the face of foreign competition. Some countries also establish flag carriers for nationalist reasons, or to aid the country's economy, particularly in the area of tourism.^{[citation needed]}