Ardeuil-et-Montfauxelles is located some 25 km south of Vouziers and 16 km east by north-east of Sommepy-Tahure on the border with the Marne department which border forms the southern border of the commune. Access is by road D6 from Manre in the west passing through the commune and the village before continuing east to Montcheutin. The smaller D121 road goes from the village north-east to join the D21 south-east of Challerange. Apart from the two villages of Ardeuil and Montfauxelles the commune is entirely farmland.
The Allin river flows through the commune from west to north-east where it continues to join the Aisne river at Brécy-Brières.
In 2009 the commune had 86 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.