Zangezur (Armenian: Զանգեզուր, Azerbaijani: Zəngəzur) is a historical and geographical region in Eastern Armenia on the slopes of the Zangezur Mountains which largely corresponds to the Syunik Province of Armenia and East Zangezur Economic Region of Azerbaijan. It was ceded to Russia by Qajar Iran according to the Treaty of Gulistan in 1813. In Soviet times, the territory of Zangezur comprised the Goris, Kapan, Meghri, and Sisian districts of the Armenian SSR and the Lachin, Qubadli, and Zangilan districts of the Azerbaijani SSR. In 1995, the Armenian districts within historical Zangezur were merged to form the Syunik Province. In Azerbaijan, the corresponding districts, while retaining their administrative status, became part of the East Zangezur Economic Region in 2021.

There are several theories about of the origin of the name Zangezur. According to Armenian scholar Ghevont Alishan, Zangezur is derived from the name of Dzagadzor fortress (now a village near Goris), which was named after a patriarch of the Sisak clan, Dzagik. Over time the name Dzagadzor changed and became Zangezur.

Some sources also mention a possible connection between the name Zangezur and another toponym—the name of the Tsakedzor gorge (Armenian: Ծակեձոր, from the Armenian tsak - "hole", dzor - "gorge, ravine") located to the northwest of Goris in the valley of the Goris River.

There are also various explanations of the name stemming from folk tradition and legends. For example, the name is interpreted as a combination of Armenian zang ("bell") and dzor ("gorge") or alternatively as zang and zor ("power"), that is, a powerful bell. There was a monastery about 2 kilometers away from Goris which had a loud bell. Another tradition connects the name with the time of the conquests of Timur. According to this tradition, an Armenian prince named Mher offered his help to Timur, saying that he will not be able to conquer Syunik as long as there is the great bell in the village of Khot which will notify the principality in case of danger. Timur promised gold and power to Mher if he would silence the bell, and the latter with his conspirators lit a fire under the bell at night, muffling its sound. When Timur's army crossed the Aras River and invaded Syunik, attempts to notify the people using the bell were in vain. The principality fell overnight, and people asked in amazement "why didn't they ring the bell?" Some answered "ringing in vain", in Armenian: “zangy zur e” (Armenian: զանգը զուր է). After that, the principality was also called Zangezur.

Historically Zangezur was the southern part of the ancient Armenian province of Syunik. A. Redgate notes that the discovery of an Athenian coin of the 6th century BC in Zangezur indicates the presence of trade relations between Armenia and Asia Minor. Inscriptions of the king of Great Armenia Artashes I (189–160 BC) have been found on the territory of Zangezur. At the beginning of the 4th century, Syunik, along with other provinces of Armenia, was converted to Christianity. Of the twelve gavars (regions) of Syunik, seven were located within Zangezur (Chaguk, Agakhechk, Gaband, Bagk or Balk, Dzork, Arevik and Kusakan). At the beginning of the 5th century, the Armenian scientist and educator Mesrop Mashtots conducted preaching and educational activities here. From 428 to the beginning of the 7th century it was a part of the Armenian province of Persia. In the middle of the 7th century, Zangezur, along with the whole of Armenia, was conquered by the Arabs.

At the end of the 9th century, Zangezur, as a part of Syunik, became a part of the Bagratid Kingdom of Armenia. Later, it became a part of the Kingdom of Syunik (this was due to the fact that in 970–980s the political center of the Syunik region began to move to the south, to the gavar of Balk).

In 1170 the Kingdom of Syunik was defeated by the Seljuks. After the expulsion of the Seljuks, an Armenian principality ruled by the Orbelians existed in this territory (in 1236 they submitted to the Mongols). The principality fell in the first half of the 15th century as a result of several invasions of Khan Tokhtamysh, Timur, the Turkoman tribes of Kara-Koyunlu, and the Timurid Shah Rukh.

In the 15th century, Zangezur fell under the rule of the Kara-Koyunlu confederation of Turkic nomadic tribes, and later under the rule of the Ak-Koyunlu. The domination of the Mongol Ilkhans and especially the Turkmen conquerors Kara-Koyunlu and Ak-Koyunlu had extremely grave consequences: the productive forces were destroyed, part of the population was plundered and exterminated, and many cultural monuments were destroyed. Lands were taken away from the local population and were settled by newcomer nomads, and part of the Armenian population was forced to emigrate from their historical lands.