Tonsure () is the practice of cutting or shaving some or all of the hair on the scalp as a sign of religious devotion or humility. The term originates from the Latin word tonsura (meaning "clipping" or "shearing") and referred to a specific practice in medieval Catholicism, abandoned by papal order in 1972. Tonsure can also refer to the secular practice of shaving all or part of the scalp to show support or sympathy, or to designate mourning. Current usage more generally refers to cutting or shaving for monks, devotees, or mystics of any religion as a symbol of their renunciation of worldly fashion and esteem.

Tonsure is still a traditional practice in Catholicism by specific religious orders (with papal permission). It is also commonly used in the Eastern Orthodox Church for newly baptised members and is frequently used for Buddhist novices, monks, and nuns. The complete shaving of one's head bald, or just shortening the hair, exists as a traditional practice in Islam after completion of the Hajj and is also practised by a number of Hindu religious orders.