Nellore is a city located on the banks of Penna River, in Nellore district of the Indian state of Andhra Pradesh. It serves as the headquarters of the district, as well as Nellore mandal and Nellore revenue division. It is the fourth most populous city in the state. It is at a distance of 279 kilometres (173 mi) from Vijayawada and about 170 km (110 mi) north of Chennai, Tamil Nadu and also about 380 km (240 mi) east-northeast of Bangalore, Karnataka.

Penna is a river of southern India. This is a unique river in world where after originating from Nandi hills, it flows as two different streams, one in North and South directions. The Penna rises in the Nandi Hills in Chikkaballapur District of Karnataka state, and runs north and east through the states of Karnataka and Andhra Pradesh to empty into bay of bengal in Andhra Pradesh. It is 597 kilometres (371 mi) long, with a drainage basin covering 55,213 km2: 6,937 km2 in Karnataka and 48,276 km2 in Andhra Pradesh. Along with this main stream there is another stream south towards Tamilnadu with the name Then Pennai or south Pennar which further moves towards the east to empty into the Bay of Bengal.The Penna river basin lies in the rain shadow region of Eastern Ghats and receives 500 mm average rainfall annually.