Ainharp (Basque: Ainharbe) is a French commune in the Pyrénées-Atlantiques department in the Aquitaine region of southwestern France.
The inhabitants of the commune are known as Ainharbars. or Ainharbear.
Ainharp is located some 50 km west by south-west of Pau, 15 km south-east of Saint-Palais, and 10 km north-west of Mauleon-Licharre. It is part of the former province of Soule.
The commune can be accessed by road D242 from Lohitzun-Oyhercq in the west passing through the village and continuing south-east to Mauleon-Licharre. The D344 road also goes to the north from the village through the commune then east to Espes-Undurein. The commune terrain is undulating of mixed farmland and forest.
Located in the drainage basin of the Adour, the commune is the source of numerous streams including the Lagardoye which forms part of the south-eastern border, the Quihilleri which forms much of the western border, and the Lafaure which forms much of the northern border.