Lake Anosy [anˈuːsi] (French: Lac Anosy) is an artificial lake in the southern part of the capital city of Madagascar, Antananarivo, about two miles south of Haute-Ville. Ampefiloha is located to the west of the lake, Isoraka to the northwest and Mahamasina to the north.

A swamp was replaced with Lake Anosy during the era of the ruler Radama I. The lake was constructed by James Cameron who gave it a shape of a heart. In the middle of the lake, there is an island connected with the city by an isthmus. On the island there is a French-built memorial to those fallen in the first world war, the Monument aux Morts made by sculptor Barberis and architect Perrin in 1927. In the Radama I era there was a gunpowder factory on the island. Later there was built a summer residence for the Queen Ranavalona I.

By the lakeside there grow jacaranda trees that flower in October and November. Great egrets used to take a rest by the lake. By the southern shore, there are barbers' kiosks. On the national independence day, June 26, an annual firework festival is arranged on the lake.

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