An abugida  /ˌɑːbuːˈɡiːdə/ (from Ge‘ez አቡጊዳ ’äbugida), also called an alphasyllabary, is a segmental writing system in which consonant–vowel sequences are written as a unit: each unit is based on a consonant letter, and vowel notation is obligatory but secondary. This contrasts with a full alphabet, in which vowels have status equal to consonants, and with an abjad, in which vowel marking is absent or optional. (In less formal treatments, all three systems are commonly called alphabets.) Abugidas include the extensive Brahmic family of scripts of South and Southeast Asia.

The term abugida was suggested by Peter T. Daniels in his 1990 typology of writing systems. It is an Ethiopian name of the Ge‘ez script, ’ä bu gi da, taken from four letters of that script the way abecedary derives from Latin a be ce de. As Daniels used the word, an abugida contrasts with a syllabary, where letters with shared consonants or vowels show no particular resemblance to each another, and with an alphabet proper, where independent letters are used to denote both consonants and vowels. The term alphasyllabary was suggested for the Indic scripts in 1997 by William Bright, following South Asian linguistic usage, to convey the idea that "they share features of both alphabet and syllabary".