The Brantas is the longest river in East Java, Indonesia.

[4] Its course is semi-circular or spiral in shape: at its source, the river heads southeast, but gradually curves south, then southwest, west, then north, and finally it flows generally eastward at the point where it branches off to become the Kalimas and Porong River.

King Mpu Sindok moved his kingdom from the Mataram Kingdom in Central Java to a new location on this river circa 950 A.D.

Possibly (only one of several reasons given) due to a Mount Merapi volcanic eruption, he had to leave his kingdom to this new safe place near the present city of Madiun.

The river flows in the eastern area of Java with a predominantly tropical monsoon climate (designated as Am in the Köppen-Geiger climate classification).