Ouanaminthe is located in the Nord-Est, or North East department of Haiti along the northern border with the Dominican Republic to the East. It has an area of 1,805 km² and a population of 300,493 people (2003).
The capital of this department is Fort-Libertè which was founded by the French in 1578. It is home to many historic sites.
The department is divided into four arrondissements: Fort-Liberté; Ouanaminthe; le Trou-du-Nord; and Vallières.