A flag carrier refers to a transportation company, such as a shipping or airline company, that is locally-registered in a given country. They may be state-run, state-owned or state-designated companies or organisations with preferential rights or privileges accorded by the government. 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 an airline) may also be known as a national airline or a national carrier, although this can have different legal meanings in some countries. In the United States for example, A national carrier (or airline) must have an annual operating revenue between $100 million and one billion.