Lake Malawi is the ninth largest lake in the world. It is 560km, 80km wide and 700m deep and forms most of the eastern border between Malawi and Mozambique. It is a fresh water lake.

The lake contains a greater variety of indigenous species of fish than any other lake in the world. World Wildlife Fund researchers have identified over 500 species to date that are not found anywhere else in the world. Most of these fish are in the cichlid family and are brightly colored and patterned.

Many Malawian villages are located on the lake shore. The lake serves as an important source of food, providing local fishermen with an abundant source of fish. A most popular dinner in Malawi is chambo (a type of fish) and nsima (a corn or cassava porridge).

Lake Malawi has traditionally provided a major food source to the residents of Malawi as it is rich in fish, the most famous of which is the Chambo, a fresh-water perch. Lake Malawi is famous for its cichlids, a group of neotropical perch-like fishes, popular in the aquarium trade. Malawi cichlids are divided into two basic groups. The first is the open-swimming, usually carnivorous species, often with colorful males and drab females, are Peacocks or Haps; the latter is short for Haplochromine, though the genus Haplochromis is now only used for a few species. The second is a group known locally and popularly known as mbuna, which means rockdweller. Mbuna are smaller, generally vegetarian, and both sexes are often quite colorful, though many species are dimorphic. The genera Maylandia and Pseudotropheus are popular cichlids for the aquarium. Cichlids are an important export for Malawi, but wild populations are increasingly threatened by commercial collecting, localized pollution and the introduction of exotic predatory species such as Nile Perch. Other wildlife resident in the lake includes abundant crocodiles, and a large population of fish eagles which feed off the fish population.

The lake also supports populations of snails some of which carry bilharzia. For many years this was strenuously denied by the government, which feared it would deter tourism in the area, but since the fall of Hastings Banda, the presence of bilharzia in the lake has been more widely acknowledged.