Pannonian Croatia (Croatian: Panonska Hrvatska), or Principality of Pannonia, also Southern Pannonia, Transsavian Croatia, or just Pannonia} is a medieval duchy from the 8th to the 10th century located in the Pannonian Plain approximately between the rivers Drava and Sava in today's Croatia, but at times also considerably to the south of the Sava.

Its capital is Sisak.

Eastern parts of the principality extend to the Syrmia region in present-day Serbia according to Hungarian historian Sándor Márki (1853-1925).