Bagneux-la-Fosse is located some 40 km east of Saint-Florentin and 15 km south-west of Bar-sur-Seine. Access to the commune is by the D32 road from Avirey-Lingey in the north which passes through the village before continuing south to join the D452 which continues to Channes. The D17 goes west from the village the north-west to Pargues. The D26 branches off the D32 north-east of the village and goes north-east to Neuville-sur-Seine. There is a large forest in the north-west of the commune and a smaller forest in the south-east with the rest of the commune farmland.
The Sarce river flows through the commune from south to north just east of the village and continues north to join the Seine at Virey-sous-Bar.
In 2010 the commune had 175 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 communes 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.