Passau (previously Latin: Batavis or Batavia) is a town in Lower Bavaria, Germany. It is also known as the Dreiflüssestadt or "City of Three Rivers," because the Danube is joined at Passau by the Inn from the south and the Ilz from the north.

Passau's population is 50,415, of whom about 10,000 are students at the local University of Passau. The university, founded in the late 1970s, is the extension of the Institute for Catholic Studies (Katholisch-Theologische Fakultät) founded in 1622. It is renowned in Germany for its institutes of Economics, Law, Theology, Computer Sciences and Cultural Studies.

In the 2nd century BC, many of the Boii tribe were pushed north across the Alps out of northern Italy by the Romans. They established a new capital called Boiodurum by the Romans, now within the Innstadt district of Passau.

Passau was an ancient Roman colony of ancient Noricum called Batavis, Latin for "for the Batavi." The Batavi were an ancient Germanic tribe often mentioned by classical authors, and they were regularly associated with the Suebian marauders, the Heruli.