Wadi al-Abyad or al-Ubayyid (Arabic: وادي الأبيض, "white wadi") is the second-longest wadi in Iraq (after Wadi Hauran) and extends in west of Iraq within Al Anbar Governorate and Karbala Governorate. It runs for roughly 250 kilometres (160 mi), from Iraqi-Saudi border (near Arar) in Al Anbar Governorate till Lake Razazah in west of Karbala Governorate. It is 1 kilometre (0.62 mi) wide,40 and 50 metres (130 and 160 ft) deep.
Often the term of Wadi al-Abyad referred to a large area including Wadi al-Abyad itself, its tributaries, and surroundings. Wadi al-Abyad is a dry place in spite of oasis called Ghadir Abu Muraji located in central part of the valley within Al Anbar Governorate in addition to some seasonal pools spread in the Wadi during rainy season. Pools and grass provide good grasslands for nomads and their livestock. In some rainy years, Wadi al-Abyad is filled with rainwater which flows into the Lake Razazah.