Bionaz is a comune sparso which extends over 143 square kilometres of the North-Eastern Valpelline area of the Aosta Valley region of northwest Italy. The commune lies on the left side of the river Dora Baltea. The population of about 240 is dispersed among 20 or more small alpine villages and hamlets including Plan-de-Veyne, which is the main centre and the capoluogo. The commune belongs to the Unité des communes valdôtaines du Grand-Combin.