Tyao River[1] (or Tiau River,[2] Tio River) is a 159 km (99 mi) long river that flows between the Mizoram state in India and the Chin State in Myanmar, forming part of the international boundary between the two countries.

[2] It rises near Khuangphah village of Champhai district in Mizoram, India.

It ultimately merges with the Kaladan River (Chhimtuipui river).

[2] The twin towns of Zokhawthar in Mizoram and Rikhawdar in Chin State are on the banks of the river.

There is an official border crossing between the two towns.