This is a list of extant towers that fulfill the engineering definition of a tower: "a tall human structure, always taller than it is wide, for public or regular operational access by humans, but not for living in or office work, and are self-supporting or free-standing, which means no guy-wires for support." The definition means the exclusion from this list of continuously habitable buildings and skyscrapers as well as radio and TV masts. Also excluded from this list because they are not designed for public or regular operational access are bridge towers or pylons, wind turbines, chimneys, transmission towers, sculptures and most large statues and obelisks.
Towers are most often built to use their height for various purposes and can stand alone or as part of a larger structure. Some common purposes are for telecommunications, and as a viewing platform.