It is legal. Though the official marriage registry only allows for one wife, it also has a clause that allows for marriage under customary law. These rules will differ depending on the community.

Which African countries allow polygamy?

Countries that recognize polygamous marriagesAlgeria.Cameroon.Chad.Central African Republic.Republic of the Congo.Djibouti.Egypt.Gabon: Both men and women can join in polygamous marriage with the other gender under Gabonese law. In practice, the right to multiple spouses is reserved for men only.More items