Barbazan is a Spa town in the Comminges region located some 13 km south-west of Saint-Gaudens and 12 km north of Cierp-Gaud. The western border of the commune is also the departmental border between Haute-Garonne and Hautes-Pyrénées. Access to the commune is by Route nationale N125 which comes from the end of the A645 autoroute and passes down the western side of the commune south to Ore. The D26E road comes from Labroquère in the north-west and passes through the north of the commune ending in the village. The D26 comes from Valcabrère in the west and passes through the village continuing to Sauveterre-de-Comminges in the east. The D33D and the D33L go south from the village to join the N125. The commune has extensive forests in the east with some farmland in the west.
The Garonne river forms most of the western border of the commune as it flows north, passing through Toulouse, to eventually join the Dordogne to form the Gironde estuary at Bordeaux. Lake Barbazan, north-west of the village at 452 m above sea level, is of glacial origin. It is surrounded by moraine deposits: sub-glacial moraine from Cumania and rocky outcrops of moraine west of the Lake. The Ruisseau de Corp flows west from the lake to join the Garonne.
Vert, 3 jets of water Argent issuant from a fountain with antique base of Or on a wave Argent mouvant from base; in chief parti per pale: at 1 Gules with 4 otelles Argent addorsed saltrirewise, at 2 Azure with a cross of Or.
In 2010 the commune had 447 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.