Hydrophis sibauensis, also known as the Kalimantan sea snake, is a species of venomous sea snake in the family Elapidae that is native to Indonesia, and endemic to Borneo. The specific epithet sibauensis refers to the Sibau River.
The species is viviparous.
The range of the snake is limited to the Sibau River, a tributary of the Kapuas River, in West Kalimantan, Borneo, in fresh water some 1,000 km upriver from the sea. The type locality is Putussibau.