Bethioua (Arabic: بطيوة) (formerly Arzew, under French rule, called Vieil Arzew then Saint Leu) is a town in the wilaya of Oran in the west of Algeria. It has a gas port, petrochemical facilities and desalination plant.
It is located on the ruins of the ancient Roman settlement of Portus Magnus. The region itself belonged to the Battiwa (pl. Ibettiwen), a group of Berber clans which arrived from the Rif mountains, mainly Ait Said tribe centuries ago in 1370. They were sent by the Merinids to defeat the Maghraouas in their capital of Mazouna but the battle they particaped failed for their side, afterwards they settled the Maghraoua territory and would not have return. Thus originally settled in Mazagran near the city of Mostaganem for nearly six centuries, when in 1784 was given to them by the bey of Mascara this coastal territory a little further west. During the French colonization, Bettiouas had to take refuge in Mazagran once again, most of them were given back their land by the authorities. Today only elders can still really speak the tribe language.
When the Anglo-Americans invaded Algeria in November 1941 (Operation Torch), the American troops who captured Oran landed at Beach Z, which was the strip of coastline between Arzew and St. Leu.