Beaufort Castle, Crusader castle in Arnoun, Lebanon

Beaufort Castle is a crusader castle in Arnoun, Lebanon, standing on a steep rocky outcrop above the Litani River. The structure includes stone walls, several towers, and defensive works that spread along the cliff edge and overlook the surrounding terrain.

Fulk, King of Jerusalem, captured the hilltop fortification in 1139 and gave it to the lords of Sidon; the Crusader castle was probably built soon after. Saladin took it in 1190 after a siege, and Baibars captured it in 1268, turning the main hall into a mosque. Fakhr al-Din II refortified it in the 17th century, but Jazzar Pasha destroyed its remaining defences in 1782.

The Crusaders' Old French name bel fort or beau fort, "beautiful fortress", survives in the Arabic Qal'at al-Shaqif, "Castle of the Steep Cliff", from shaqif, a word borrowed from Aramaic for a rock that drops sharply from a mountain. The castle also carries the name Shaqif Arnun, after the village of Arnoun below it.

The castle sits on a 300-metre cliff that drops steeply eastwards to the Litani River, about 1 km south-south-east of Arnoun. Although it lies only 5 km from the Israeli border, the steep slope forces a long, winding approach, and the final stretch climbs a narrow, exposed gradient. The site is ruined and partly damaged by shelling, so footing among the fallen blocks is uneven.

A Roman lookout tower stood on the hill long before the castle; the site's strategic value was recognised in Roman times. T. E. Lawrence visited in 1909 during his walk across Lebanon and Syria and was struck by the view of the coast and the Litani River.