The Republic of Madagascar comprises the island of Madagascar which, at 587,000 square kilometres (227,000 sq mi), is classified as the fourth-largest island in the world,  as well as numerous smaller peripheral islands. 
The island was once a part of the suthern "supercontinent" of Gondwana, together with India, Antarctica, Africa and South America. It split  rom India around 88 million years ago, allowing plants and animals on the island to evolve in complete isolation.  Consequently, Madagascar is a biodiversity hotspot in which over 80% of its plant and animal species are found nowhere else on Earth.  Its most known kind of fauna are the  lemurs. 

In fiction (and comics) Madagascar is sometimes identified with the remaining part of the lost continent of Lemuria.