3. Madagascar
Madagascar ranks third on our list of most ethnically diverse countries in the world in 2018, and it is certainly very ethnically diverse but about nine-tenths of the entire population is Malagasy, divided into 20 different ethnic groups, according to Britannica. The most dominant groups among them are the Merina people with the second largest group being the Betsimisaraka. Other important groups include the Tsimihety, the Sakalava, the Antandroy, the Tanala, etc. According to the same source, about two-fifths of the population practices the traditional religion based on ancestor worship. Protestantism and Roman Catholicism are also widespread with about half the population being Christian. There is a small percent of Sunni Muslim as well.