Basar is a census town situated in the administrative district of West Siang in the state of Arunachal Pradesh in India. The district headquarters are in the town of along. The district spreads over an area of 8325 square km and has a total population of 103,575 (as per the India census of 2001). Different tribal groups of the district are the Adi, Memba and Khamba. A famous Tibetan Buddhist temple, Mechuka Gompa, is positioned in the western part of the Mechuka district of West Siang.

The exact geographical location of Basar is at 27.98° North and 94.67° East. It has a mean elevation of 579 metres (1899 feet). According to the 2001 India census, Basar has a population of 3834. Males make up 56% of the population and females form 44%. Basar has a mean literacy rate of 72%, higher than the countrywide mean of 59.5%. 61% of the males and 39% of the females are literate. 16% of the population is made up of children less than 6 years of age.