Baybayin (pre-kudlit: ᜊᜊᜌᜒ, post-kudlit: ᜊᜌ᜔ᜊᜌᜒᜈ᜔) (known in Unicode as Tagalog script; see below), is a pre-Spanish Philippine writing system. It is a member of the Brahmic family and is recorded as being in use in the 16th century. It continued to be used during the Spanish colonization of the Philippines up until the late 19th Century.^{[citation needed]}

The term Baybay literally means "to spell" in Tagalog. Baybayin was extensively documented by the Spanish. Some have attributed it the name Alibata, but this name is incorrect. (The term "Alibata" was coined by Paul Rodríguez Verzosa after the arrangement of letters of the Arabic alphabet alif, ba, ta (alibata), “f” having been eliminated for euphony's sake." )

Modern scripts in the Philippines, descended from Baybayin, are Hanunó'o, Buhid, Tagbanwa and Kapampangan script.

Baybayin is one of a number individual writing systems used in Southeast Asia, nearly all of which are abugidas where any consonant is pronounced with the inherent vowel a following it— diacritical marks being used to express other vowels (this vowel occurs with greatest frequency in Sanskrit, and also probably in all Philippine languages). Many of these writing systems descended from ancient scripts used in India over 2000 years ago. Although the baybayin does share some, there is no evidence that it is this old.