The Baïse (pronounced: [baiːz]) (Occitan: Baïsa) is a 188-kilometre (117 mi) long river in south-western France, left tributary of the Garonne. Its source is in the foothills of the Pyrenees, near Lannemezan. It flows north through the following départements and towns: Hautes-Pyrénées: Lannemezan, Trie-sur-Baïse Gers: Mirande, Castéra-Verduzan, Valence-sur-Baïse, Condom Lot-et-Garonne: Nérac, LavardacIt flows into the Garonne near Aiguillon.