West Siang district is an administrative district in the state of Arunachal Pradesh in India.

Arunachal Pradesh is a state in northeast India. It was formed from the North-East Frontier Agency (NEFA) region, and India declared it as a state on 20 February 1987. Itanagar is its capital and largest town. It borders the Indian states of Assam and Nagaland to the south. It shares international borders with Bhutan in the west, Myanmar in the east, and a disputed 1,129 km border with China's Tibet Autonomous Region in the north at the McMahon Line.