South India is a peninsula in the shape of a vast inverted triangle, bounded on the west by the Arabian Sea, on the east by the Bay of Bengal and on the north by the Vindhya and Satpura ranges. The line created by the Narmada River and Mahanadi river is the traditional boundary between northern and southern India.

The Narmada flows westwards in the depression between the Vindhya and Satpura ranges. The Satpura ranges define the northern spur of the Deccan plateau, one of the main geographic features of South India. The Western Ghats, along the western coast, mark another boundary of the plateau. The narrow strip of verdant land between the Western Ghats and the Arabian Sea is the Konkan region; the term encompasses the area south of the Narmada as far as Goa.

The Western Ghats continue south, forming the Malnad (Canara) region along the Karnataka coast, and terminate at the Nilgiri mountains, an inward (easterly) extension of the Western Ghats. The Nilgiris run in a crescent approximately along the borders of Tamil Nadu with northern Kerala and Karnataka, encompassing the Palakkad and Wayanad hills, and the Satyamangalam ranges, and extending on to the relatively low-lying hills of the Eastern Ghats, on the western portion of the Tamil Nadu-Andhra Pradesh border. The Tirupati and Annamalai hills form part of this range.

The Deccan plateau, covering the major portion of the states of Maharashtra, Karnataka and Tamil Nadu, is the vast elevated region bound by the C-shape defined by all these mountain ranges. No major elevations border the plateau to the east, and it slopes gently from the Western Ghats to the eastern coast. The plateau is watered by the east flowing Godavari and Krishna rivers. The other major rivers of the Deccan plateau are the Pennar and the Tungabhadra, a major tributary of the Krishna.

The river Kaveri rises in the Western Ghats, in the Kodagu district of Karnataka and flows briefly through the Deccan plateau before entering Tamil Nadu, where it forms an extensive and fertile delta on the east coast. The three major river deltas of South India, the Kaveri, the Godavari and the Krishna, are located along the Bay of Bengal. These areas constitute the rice bowls of South India. Rivers that flow westward, from the mountains to the Arabian Sea, include the Periyar, Netravati River, Mandovi and Tapti River (or Tapi) rivers, and the Narmada at the northern edge of the region.