The Saison[1] (French pronunciation: [sɛzɔ̃] ⓘ) or Uhaitz Handia[2] is a left tributary of the Gave d'Oloron river in the French Basque Country, (Pyrénées-Atlantiques), Southwest of France.

Its general south to north direction provides the axis for the former French province of Soule.

It is 72.2 km (44.9 mi) long, including its upper courses Zurkaitzegiko erreka and Gave de Larrau.

[3] The river is formed in Licq-Athérey from the confluence of the Gave de Sainte-Engrâce (from the Pierre-Saint-Martin Cave) and the Gave de Larrau (from the Pic d'Orhy).

It flows north and joins the Gave d'Oloron in Autevielle-Saint-Martin-Bideren, downstream from Sauveterre-de-Béarn.