The Kerala backwaters are a chain of brackish lagoons and lakes lying parallel to the Arabian Sea coast (known as the Malabar Coast) of Kerala state in southern India. The network includes five large lakes linked by canals, both manmade and natural, fed by 38 rivers, and extending virtually half the length of Kerala state. The backwaters were formed by the action of waves and shore currents creating low barrier islands across the mouths of the many rivers flowing down from the Western Ghats range.

Kerala has over 900 km of interconnected waterways, rivers, lakes and inlets that make up the Kerala backwaters. In the midst of this beautiful landscape there are a number of towns and cities, which are the starting and end points of backwater cruises. National Waterway No. 3 from Kollam to Kottapuram, covers a distance of 205 km and runs almost parallel to the coast line of southern Kerala facilitating both cargo movement and backwater tourism. Ayub, Akber (ed), Kerala: Maps & More, Backwaters, 2006 edition 2007 reprint, pp. 40-53, Stark World Publishing, Bangalore, ISBN 81-902505-2-3

The backwaters have a unique ecosystem - freshwater from the rivers meets the seawater from the Arabian Sea. In certain areas, such as the Vembanad Kayal, where a barrage has been built near Kumarakom, salt water from the sea is prevented from entering the deep inside, keeping the fresh water intact. Such fresh water is extensively used for irrigation purposes.

Many unique species of aquatic life including crabs, frogs and mudskippers, water birds such as terns, kingfishers, darters and cormorants, and animals such as otters and turtles live in and alongside the backwaters. Palm trees, pandanus shrubs, various leafy plants and bushes grow alongside the backwaters, providing a green hue to the surrounding landscape.

Vembanad Kayal is the largest of the lakes, covering an area of 200 km², and bordered by Alappuzha (Alleppey), Kottayam, and Ernakulam districts. The port of Kochi (Cochin) is located at the lake's outlet to the Arabian Sea. Alleppey, "Venice of the East", has a large network of canals that meander through the town. Vembanad is India’s longest lake.