The Serayu River is a river in Central Java, Indonesia, about 300 km southeast of the capital Jakarta.

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

The warmest month is March, when the average temperature is around 25 °C, and the coldest is August, at 23 °C.

The wettest month is January, with an average of 561 mm of rainfall, and the driest is September, with 34 mm of rainfall.

[9][10] Water rafting is one of the tourist attractions in the villages of Tunggara and Prigi, in Banjarnegara Regency.