The Portuguese were the first European to settle down there. Porto Novo is also known as Ajase (Ajace) by the Yorubas, and known as Hogbonu by the Ogu.
Porto Novo was established in the 16th Century. It was a Slave port controlled by the Alaafin of Oyo. The Oyo Empire was a great empire which also controlled the Slave port of Badagry. It partly controlled the Slave port of Whydah (Ouidah) for a period before Whydah was completely taken over by the Dahomey Kings.