Tyao River (or Tiau River, Tio River) 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.

It rises near Khuangphah village of Champhai district in Mizoram, India. It ultimately merges with the Kaladan River (Chhimtuipui river).

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.