The Kaveri (also known as Cauvery, Tamil: [kɑːʋɪɾi]) is a major river flowing across Southern India. It is the third largest river in the region after Godavari and Krishna. The catchment area of the Kaveri basin is estimated to be 81,155 km² (31,334 sq mi) and encompasses the states of Tamil Nadu, Karnataka, Kerala, and the union territory of Puducherry.

The river rises at Talakaveri in the Brahmagiri range in the Western Ghats. The source is located at an elevation of 1,341 m (4,400 ft) in the Kodagu district of Karnataka. The river flows for about 320 km (200 mi) through the Deccan plateau in Karnataka before entering Tamil Nadu. It flows further eastward in Tamil Nadu for 416 km (258 mi) before flowing into the Bay of Bengal near Poompuhar in Mayiladuthurai district of Tamil Nadu. The river flows for a total length of about 800 km (500 mi). The major tributaries include Amaravati, Arkavati, Bhavani, Harangi, Hemavati, Kabini, Lakshmana Tirtha, Shimsha and Noyyal.

There are a number of dams on the river which form part of an extensive irrigation system and are used for the generation of hydroelectric power. The river has supported agriculture for centuries and has served as the lifeline of several kingdoms in the past. Access to the river's waters has been a cause of dispute among the states of Karnataka and Tamil Nadu for decades. The Kaveri basin is a densely populated region, with several towns and cities located on its banks.

The river is considered as sacred by the people of Southern India and is considered to be among the seven holy rivers of India. The river is often personified and worshiped as the goddess Kaveri. The river is mentioned in various Hindu religious texts including the Mahabharata and the Puranas. In ancient Tamil literature, the river is referenced to as Ponni meaning "the golden one".

Kaveri is mentioned in Sanskrit as a holy river in various Hindu religious texts including the Mahabharata and the Puranas. The name itself might have had different etymologies. As per Skanda Purana, the river arose after Ganesha took a form of a crow and toppled sage Agastya's kamandala. The river then took its name from the Tamil language words kā meaning "crow" and viri meaning "spread" literally translating to "spread by a crow". It might also mean a river with wide spread banks as viri can also be translated as wide spread. The etymology of the river might have also been derived from kāviri, the Sankethi word for "river" from the language spoken by the Sankethi people, who live along its waters. Cauvery is the anglicized version of the original name.

The river is also known by other names. In ancient Tamil literature, the river was called Ponni meaning "the golden one" in reference to the fine silt it deposits. It is known as Daksina gaṅgā meaning the "Ganges of the South" indicating its geographical location and its significance. It is also mentioned as Ardha gaṅgā meaning Half Ganga in Mahabharata and other literature, due to its purported mythology of having arisen from the Ganges. Marudvṛdhā is another hypothesised name for this river, meaning "the beloved of the Maruts" in Sanskrit.

The river arises at Talakaveri in Kodagu district of Karnataka. The source of the river is located at an altitude of 1,341 m (4,400 ft) in the Brahmagiri Hills of the Western Ghats. Its follows a rough upper course consisting of rocky beds and high banks. Once it leaves the Kodagu hills, it flows eastwards and forms a series of rapids and falls. It flows through a narrow gorge onto the Deccan plateau and drops about 18–24 m (59–79 ft) at Chunchanakatte Falls. The river forms the island of Srirangapatna and widens to 900–1,200 ft (270–370 m) before flowing south-east. At Shivanasamudra, the river drops 91 m (299 ft) and forms the Shivanasamudra Falls, one of the largest waterfalls in the country. After forming the island of Shivanasamudra, the river converges and passes through the Mekedatu gorge. After flowing for 320 km (200 mi) in Karnataka, the river flows for about 64 km (40 mi) along the Karnataka-Tamil Nadu border.

The river enters Tamil Nadu and forms the Hogenakkal Falls. After the falls, the river flows southwards towards Mettur Dam and joins its main right bank tributary Bhavani at Kooduthurai. The river flows eastwards through Erode and Karur, and widens further before entering the Tiruchirappalli district. It splits into two branches with the northern part called as Kollidam River and the southern part of the river retaining the name Kaveri. After flowing for 16 km (9.9 mi), the two branches converge around the Srirangam island. The river further branches off into 36 different channels before emptying into the Bay of Bengal near Poompuhar in Mayiladuthurai district. The river traverses for about 416 km (258 mi) in Tamil Nadu for a total length of about 800 km (500 mi).