A fortified French town, trading and manufacturing, in the dep. of Basses-Pyrénées, at the confluence of the Adour and Nive, 4 m. from the Bay of Biscay; noted for its strong citadel, constructed by Vauban, and one of his chef-d'oeuvres, and its 12th-century cathedral church; it belonged to the English from 1152 to 1451.