Bosnian (bosanski [bɔ̌sanskiː], Cyrillic: босански) is a form of Serbo-Croatian, a South Slavic language, spoken by Bosniaks. As a standardized form of the Shtokavian dialect, it is one of the three official languages of Bosnia and Herzegovina.

The same subdialect of Shtokavian is also the basis of standard Croatian and Serbian, so all are mutually intelligible. Up until the dissolution of former SFR Yugoslavia, they were treated as a unitary Serbo-Croatian language, and that term is still used to refer to the common base (vocabulary, grammar and syntax) of what are today officially four national standards. The Bosnian standard uses both Latin and Cyrillic alphabets.

The first official dictionary in the Bosnian language was printed in the early 1630s, while, comparatively, the first dictionary in Serbian was printed only in the mid-19th century. Written evidence and records point to the Bosnian language being the official language of the country since at least the Kingdom of Bosnia, as further corroborated by the declaration of the Charter of Ban Kulin, one of the oldest written state documents in the Balkans and one of the oldest to be written in Bosančica.