Arzay is located some 27 km east by south-east of Vienne and 25 km south of Villefontaine. Access to the commune is by the minor D51 road (Route de Beaurepaire) from Pommier-de-Beaurepaire in the south-west passing through the heart of the commune south of the village and continuing to Semons in the east. Access to the village can be by several country roads running off the D51 including the Chemin de la Grande Fontaine, the Chemin de la Croix, or the Chemin de la Diligence. The hilly part of the commune north of the village is heavily forested (part of the Forest of Bonnevaux) while the flat commune south of the village is farmland.
A band of "Étangs" - ponds or lakes - crosses the commune in the north from south-west to north-east. The Étangs within the commune are:
Étang du Grand Albert,
Étang du Grand Massot,
Étang du Petit Massot,
Étang de Clos Gabet,
Étang de la Chapelle,
The Suzon river flows through the south of the commune from east to west and continues south-west to eventually join the Oron at Beaurepaire. The Grande Vareze flows into the largest of the Étangs in the north - the Étang du Grand Albert.
In 2010 the commune had 216 inhabitants. The evolution of the number of inhabitants is known from the population censuses conducted in the commune since 1793. From the 21st century, a census of communes with fewer than 10,000 inhabitants is held every five years, unlike larger towns that have a sample survey every year.[Note 1]
^At the beginning of the 21st century, the methods of identification have been modified by Law No. 2002-276 of 27 February 2002, the so-called "law of local democracy" and in particular Title V "census operations" allows, after a transitional period running from 2004 to 2008, the annual publication of the legal population of the different French administrative districts. For communes with a population greater than 10,000 inhabitants, a sample survey is conducted annually, the entire territory of these communes is taken into account at the end of the period of five years. The first "legal population" after 1999 under this new law came into force in 1 January 2009 and was based on the census of 2006.