In many countries, a mayor is the highest-ranking official in a municipal government such as that of a city or a town. Worldwide, there is a wide variance in local laws and customs regarding the powers and responsibilities of a mayor as well as the means by which a mayor is elected or otherwise mandated. Depending on the system chosen, a mayor may be the chief executive officer of the municipal government, may simply chair a multi-member governing body with little or no independent power, or may play a solely ceremonial role. A mayor's duties and responsibilities may be to appoint and oversee municipal managers and employees, provide basic governmental services to constituents, and execute the laws and ordinances passed by a municipal governing body (or mandated by a state, territorial or national governing body). Options for selection of a mayor include direct election by the public, or selection by an elected governing council or board.

The term mayor shares a linguistic origin with the military rank of Major, both ultimately derived from French majeur.