A cedilla (Spanish) ( /sɨˈdɪlə/ si-DIL-ə), also known as cedilha (Portuguese) or cédille (French), is a hook or a tail ( ¸ ) added under certain letters as a diacritical mark to modify their pronunciation.

The tail originated in Spain as the bottom half of a miniature cursive z. The word "cedilla" is the diminutive of the Old Spanish name for this letter, ceda (zeta). Modern Spanish, however, no longer uses this diacritic, although it is still current in Portuguese,Catalan, Occitan, and French, which gives English the alternative spellings of cedille, from French "cédille", and the Portuguese form cedilha. An obsolete spelling of cedilla is cerilla. The earliest use in English cited by the Oxford English Dictionary is a 1599 Spanish-English dictionary and grammar. Chambers' Cyclopædia is cited for the printer-trade variant ceceril in use in 1738. The main use in English is not universal and applies to loan words from French and Portuguese such as "cachaça", "limaçon" and "façade" (often typed "cachaca", "limacon" and "facade" due to lack of Ç keys on the keyboards of most Anglophone countries).