Ouémé is one of the twelve departments of Benin, containing the capital of the country Porto Novo, named for the Ouémé River. It is subdivided into nine communes, each centred at one of the principal towns: Adjarra, Adjohoun, Aguégués, Akpro-Missérété, Avrankou, Bonou, Dangbo, Porto-Novo and Sèmè-Kpodji. In 1999, the northern section of Ouémé was split off to form the department of Plateau.

Porto-Novo is the capital and second-largest city of Benin. The commune covers an area of 110 square kilometres (42 sq mi) and as of 2002 had a population of 223,552 people.