muḥāfaẓah (governorate) of the Nile River delta, Lower Egypt. It embraces the whole of the delta west of the Rosetta Branch, with a considerable desert region to the south. The capital and largest city is Damanhūr; other principal towns are Idkū, Kafr Salim, and Rosetta (Rashīd), where the Rosetta Stone was discovered. The area's political history dates from the division of Egypt into provinces by the Fāṭimid caliph al-Mustanṣir (ruled AD 1036–94), when Damanhūr was made its capital.

Agriculture is the principal occupation of the delta portion of the governorate; long-staple cotton is the major crop. Rice, other cereals, potatoes, sugar beets, onions, peanuts (groundnuts), tomatoes, and sesame are also harvested, and there are vineyards near Alexandria. The barrage on the Rosetta Branch at Idfīnā, 12 miles (20 km) southeast of Rosetta, supplies irrigation water during the low (winter) season and also prevents seawater from entering the irrigation channels. Along the Al-Nubāriyah Canal, in the western part of the governorate, a large reclamation project has converted unproductive land to vegetable-producing farmland. The Taḥrīr Authority has also undertaken an extensive agricultural reclamation project in the far western part of the governorate, which includes housing projects and health clinics. Natron (hydrated sodium carbonate) is obtained from the lake-dotted depression of Gharrāqat al-Barnūjī, 12 miles (19 km) south of Damanhūr, and from the Al-Naṭrūn Wadi, in the southwestern desert area. At Kafr al-Dawwār southeast of Alexandria there are cellophane and textile mills. In the mid-1970s a major natural-gas deposit was discovered offshore in Abū Qīr Bay, and it has since been developed to power industries in the northern part of Al-Buḥayrah governorate and in Alexandria. The governorate is crossed by two Suez-Mediterranean oil pipelines. Sadat City, 57 miles (92 km) northwest of Cairo, was built in the late 1970s on the Fuʾād al-Auwa desert highway to house new industries and also to relieve the overpopulation of Cairo.

At Kawm Juʿayf are the ruins of ancient Naukratis, a Greek trading centre that flourished in the 6th century BC. A railway along the north coast links Alexandria to Rosetta and Idfīnā; the Cairo–Alexandria highway with a railway parallel to it crosses the governorate. The newer Fuʾād al-Auwa limited-access highway crosses the desert in western Al-Buḥayrah governorate, bypassing the densely populated delta region. Area 3,911 square miles (10,130 square km). Pop. (2006) 4,737,129.