Bister is a municipality in the district of Raron in the canton of Valais in Switzerland .

Bister is first mentioned in 1374 as Bystur. In 1480 it was mentioned as Bistar.

Bister has an area, as of 2011, of 5.8 square kilometers (2.2 sq mi). Of this area, 18.4% is used for agricultural purposes, while 40.0% is forested. Of the rest of the land, 0.3% is settled (buildings or roads) and 41.3% is unproductive land.