Hermann II (early 1360s – October 13, 1435), Count of Celje, is a Styrian nobleman and magnate most notable as the faithful supporter and father-in-law of the Hungarian king Sigismund of Luxembourg.

Hermann's loyalty to the King ensures him generous grants of land and privileges that lead him to become the greatest landowner in the Croatian lands.

He serves twice as ban of the combined provinces of Slavonia, Croatia and Dalmatia, and is recognized by a treaty in 1427 as heir presumptive to the Kingdom of Bosnia.

The House of Celje's rise to power culminatea in achieving the dignity of Prince of the Holy Roman Empire.

Hermann is the most important representative of the line of Celje counts, having brought the family from merely local importance to the focus of Central European politics.