A bell tower is a tower that contains one or more bells, or that is designed to hold bells even if it has none. Such a tower commonly serves as part of a Christian church, and will contain church bells, but there are also many secular bell towers, often part of a municipal building, an educational establishment, or a tower built specifically to house a carillon. Church bell towers often incorporate clocks, and secular towers usually do, as a public service.

The term campanile (, also US: , Italian: [kampaˈniːle]), from the Italian campanile, which in turn derives from campana, meaning "bell", is synonymous with bell tower; though in English usage campanile tends to be used to refer to a free standing bell tower. A bell tower may also in some traditions be called a belfry, though this term may also refer specifically to the substructure that houses the bells and the ringers rather than the complete tower.

The tallest free-standing bell tower in the world, 113.2 metres (371 ft) high, is the Mortegliano Bell Tower, in the Friuli Venezia Giulia region, Italy.