Greater Croatia (Croatian: Velika Hrvatska) is a term applied to certain currents within Croatian nationalism. In one sense, it refers to the territorial scope of the Croatian people, emphasising the ethnicity of those Croats living outside Croatia. In the political sense, though, the term refers to an irredentist belief in the equivalence between the territorial scope of the Croatian people and that of the Croatian state.
The concept of a Greater Croatian state has its modern origins with the Illyrian movement, 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. Although this movement arose in the developing European nationalist context of the time, it particularly arose as a response to the more powerful nationalist stirrings in the then-Kingdom of Hungary, of which Croatia was a part.
The foundations of the concept of Greater Croatia are laid in late 17th and early 18th century works of Pavao Ritter Vitezović. He was the first ideologist of Croatian nation who proclaimed that all Slavs are Croats. His works were used to legitimize expansionism of the Habsburg Empire to the east and south by asserting its historical rights to claim Illyria. "Illyria" as Slavic territory projected by Vitezović would eventually incorporate not only most of the Southeastern Europe but also parts of Central Europe such as Hungary. Vitezović defines territory of Croatia which, besides Illyria and all Slavic populated territory, includes all the territory between Adriatic, Black and Baltic seas.