Arbaz is a municipality in the district of Sion in the canton of Valais in Switzerland .

Arbaz is first mentioned about 1185 as Alba. In 1338 it was mentioned as Arba.

Arbaz has an area, as of 2009, of 19.3 square kilometers (7.5 sq mi). Of this area, 4.25 km2 (1.64 sq mi) or 22.0% is used for agricultural purposes, while 4.83 km2 (1.86 sq mi) or 25.0% is forested. Of the rest of the land, 0.99 km2 (0.38 sq mi) or 5.1% is settled (buildings or roads), 0.06 km2 (15 acres) or 0.3% is either rivers or lakes and 9.15 km2 (3.53 sq mi) or 47.4% is unproductive land.