Alleuze is located some 7 km due south of Saint-Flour on the edge of the Planèze plateau. Access to the commune is by a number of minor roads including the D48 from Lavastrie in the west changing to the D40 in the commune then passing north through a circuitous route in the heart of the commune to the village and continuing north-west to the hamlet of Barry before continuing north to Saint-Flour. There is also the D116 from the village to the north-west. The eastern and north-eastern borders of the commune consist of the lake formed by the Barrage of Grandval which was formed from the Truyère river. Apart from the village there are also the hamlets of Barry and Vedrines. Much of the commune is farmland but with considerable forests next to the lake and in the south.
Numerous streams rise in the commune and flow eastwards to the Barrage of Grandval Lake. These include the Ruisseau de Larcher, the Alleuze, the Ruisseau de la Bastide, the Ruissseau de la Barge, the Ruisseau de Labaisse, the Ruisseau de Mouguenoux, the Ruyisseau de Sartio, and the Ruisseau de Levert.
In 2009 the commune had 207 inhabitants. The evolution of the number of inhabitants is known through 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" which allow, after a transitional period running from 2004 to 2008, the annual publication of the legal population of the different French administrative districts. For municipalities with a population greater than 10,000 inhabitants, a sample survey is conducted annually, the entire territory of these municipalities 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 on 1 January 2009 and was based on the census of 2006.