A common carrier in common law countries (corresponding to a public carrier in some civil law systems, usually called simply a carrier) is a person or company that transports goods or people for any person or company and is responsible for any possible loss of the goods during transport. A common carrier offers its services to the general public under license or authority provided by a regulatory body, which has usually been granted "ministerial authority" by the legislation that created it. The regulatory body may create, interpret, and enforce its regulations upon the common carrier (subject to judicial review) with independence and finality as long as it acts within the bounds of the enabling legislation.

A common carrier (also called a public carrier in British English) is distinguished from a contract carrier, which is a carrier that transports goods for only a certain number of clients and that can refuse to transport goods for anyone else, and from a private carrier. A common carrier holds itself out to provide service to the general public without discrimination (to meet the needs of the regulator's quasi judicial role of impartiality toward the public's interest) for the "public convenience and necessity." A common carrier must further demonstrate to the regulator that it is "fit, willing, and able" to provide those services for which it is granted authority. Common carriers typically transport persons or goods according to defined and published routes, time schedules, and rate tables upon the approval of regulators. Public airlines, railroads, bus lines, taxicab companies, phone companies, internet service providers, cruise ships, motor carriers (i.e., canal operating companies, trucking companies), and other freight companies generally operate as common carriers. Under US law, an ocean freight forwarder cannot act as a common carrier.

The term common carrier is a common law term and is seldom used in Continental Europe because it has no exact equivalent in civil-law systems. In Continental Europe, the functional equivalent of a common carrier is referred to as a public carrier or simply as a carrier. However, public carrier in Continental Europe is different from public carrier in British English in which it is a synonym for contract carrier.