The Illyrian movement (Croatian: Ilirski pokret, Slovene: Ilirsko gibanje) was a pan-South-Slavist cultural and political campaign with roots in the early modern period, and revived by a group of young Croatian intellectuals during the first half of the 19th century, around the years of 1835–1849 (there is some disagreement regarding the official dates). This movement aimed to create a Croatian national establishment in Austria-Hungary through linguistic and ethnic unity, and through it lay the foundation for cultural and linguistic unification of all South Slavs under the revived umbrella term Illyrian.
Aspects of the movement pertaining to the development of Croatian culture are considered in Croatian historiography to be part of the Croatian National Revival (Hrvatski narodni preporod).
In the 19th century, the name Illyrian was chosen by the members of the movement as a reference to the theory according to which South Slavs descend from ancient Illyrians. Fearing provincial particularism, reformers believed that the Illyrian name would make it easier to implement literary unity.