Lake Alaotra, also Lac Alaotra, is Madagascar's largest lake, and forms the center of the island's most important rice-growing region. It is a rich habitat for wildlife, including some rare and endangered species, as well as an important fishing ground. Lake Alaotra and its surrounding wetlands cover 7,225 km², and include a range of habitats, including open water, reedbeds, marshes, and rice paddies. Lake Alaotra was declared a wetland of international importance under the international Ramsar Convention on February 2, 2003.

The fertile plain surrounding lake Lake Alaotra is Madagascar's most important rice-producing region. The hills surrounding the lake were formerly forested, but have mostly been cleared for farmland in past decades. Severe erosion on these vulnerable hill slopes has caused considerable sedimentation of the lake, which is fast disappearing; the lake is now only 60 cm (two feet) deep during the dry season. Pressure to create more rice fields has also led locals to burn the reedbeds surrounding the lake. These reedbeds provide the sole habitat of the endemic Alaotra Gentle Lemur (Hapalemur griseus alotrensis). The Alaotra Gentle Lemur is now limited to only 220 km² of remaining reedbeds, and in recent years the lemur population rapidly declined by 60%, from approximately 7,500 individuals in 1994 to 3,000 in 2001, mostly from habitat loss, but also from hunting by local villagers.

The lake is also an important but increasingly threatened habitat for waterbirds, including the endangered Meller’s Duck (Anas melleri). Two waterbird species endemic to the lake, the Madagascar pochard (Aythya innotata) and Alaotra Grebe (Tachybaptus rufolavatus, also known as Delacour's Little Grebe or Rusty Grebe) are critically endangered, and possibly extinct.