The Union Territory of Pondicherry consists of four regions, viz Pondicherry, Karaikal, Mahe, and Yanam. All the four regions are at different locations isolated from one another. Pondicherry region, which is the largest of all the four, lies on the East coast, consisting of 12 scattered areas lying in between 11^o42^' and 12^o30^'N and between 76^o36^'and 70^o53^'E. Karaikal region is about 150 km south of Pondicherry and is surrounded by Nagapattinam District of Tamil Nadu. It is located between 10^o49^'and 11^o01^'N and 79^o43^' and 79^o52^'E. Yanam region is located between 16^o42^' and 16^o46^'N and 82^o11^'and 82^o19^'E. at about 840 km east of Pondicherry near Kakinanda in Andhra Pradesh. Mahe region lies almost parallel to Pondicherry between 11^o42^'and 11^o43^'N and 75 ^o31^' and 75^o33^'E at 653 km away on the west coast near Tellicherry in Kerala. The first three regions are located on the coast of Bay of Bengal while Mahe is on the west coast of India. The three regions receive an average rainfall of about 127 cm from both the South west and North east monsoon and the average temperature is 28^oC; average humidity is 80%. Mahe receives showers only from south-west monsoon and receives more rainfall than the other three regions. These are situated well in the tropics near 12^oN are greatly influenced by hot and humid tropical maritime type of climate.

The main entity i.e Pondicherry is almost a semicircle comprising 292 km² ranging between 11^o46^' and 12^o3^'N and between 79^o 53^'E. In general, the Pondicherry region is flat and at the average elevation of 15 m above sea level and it is intersected by the deltaic channels of rivers Gingee and Ponniyar and other streams forming two main drainage basins interspread with lagoon, lakes and tanks. Superficially the coast is sandy and the border has a length of 22 km.