Beth Kustan (Arabic: باقسيان; Syriac: ܒܝܬ ܩܣܝܢܐ;[2] Turkish: Alagöz; Bethkustan)[1][a] is a neighbourhood of the municipality and district of Midyat, Mardin Province in Turkey.

[11] It has been suggested that the village was founded by a member of the Roman limitanei (frontier militia) named Constans in the 4th century AD.

[13] Philoxenus Yeshu, metropolitan bishop of the Monastery of the Cross and Hah (r. 1368–1410), ordained by Ignatius Saba I, patriarch of Tur Abdin, was from Beth Kustan.

[17] Amidst the Sayfo, Hajo, chief of the Kurtak clan, escorted the villagers to safety at Hah, where they stayed for seven years until they were able to return to Beth Kustan with the help of Çelebi Ağa of the Haverkan confederation.

[5] Most of the village's population were forced to leave in the 1960s and 1970s due to the Kurdish–Turkish conflict and emigrated abroad to the Netherlands, Germany, and Switzerland.