Astaillac is located some 45 km south-east of Brive-la-Gaillarde and 15 km north by north-west of Saint-Céré. The eastern border of the commune is also the border between the departments of Corrèze and Lot. Access to the commune is by the D41 road from Beaulieu-sur-Dordogne in the north passing through the east of the commune and continuing south-west to Liourdres. The D41E1 comes from the D153E south-west of Sioniac through the commune to the village and continues to the hamlet of La Plaine. Apart from the village there are the hamlets of Conques, Le Soulie, La Plaine, and Cassagne. The commune is mixed forest and farmland.
The Dordogne river forms the eastern border of the commune except for a small area on the left bank which forms part of the commune. The Dordogne flows south and eventually joins the Garonne at Saint-Seurin-de-Bourg. Several streams rise in the commune and flow south-east to join the Dordogne: the Ruisseau de Ganissal, the Ruisseau de Fontanille, the Ruisseau de Laborie, and the Ruisseau de Coucoulogne which forms the western border of the commune.
In 2010 the commune had 221 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 on 1 January 2009 and was based on the census of 2006.