Rumkale (lit. 'Roman Castle'; Armenian: Հռոմկլա, romanized: Hromgla) is a ruined fortress on the Euphrates, located in the province of Gaziantep and 50 km west of Şanlıurfa.

Although Rumkale is sometimes linked with places mentioned in ancient sources, the foundations of the structure can be traced back to the Byzantine rule the earliest, when the fortress was the seat of a Syriac Orthodox bishopric. Rumkale evolved into a town when its Armenian civilian population grew in the 11th century. The fortress slipped away from the Byzantine rule when Philaretos Brachamios (r. 1071–1087), a Byzantine general of Armenian origin, usurped control of the region amidst the political turmoil caused by the Battle of Manzikert in 1071. Rumkale then came under Kogh Vasil, whose adoptive son and successor Vasil Dgha was tortured by Baldwin II of Edessa and forced to relinquish his lands, including Rumkale, to the Crusader states in 1116. Sometime between 1148 and 1150, Catholicos Grigor III Pahlavuni purchased the fortress making it the headquarters of the Armenian Apostolic Church, although it continued to house Syriac Orthodox and Catholic representatives. The town later became part of the Armenian Kingdom of Cilicia, and by 1268, became isolated from the rest of the Cilician domains.

In 1292, the castle was besieged and captured by the Mamluk Sultanate. From then on, it served as a significant outpost on the border with the Ilkhanate, a breakaway state of the Mongol Empire. In 1516, Rumkale surrendered to the Ottoman army without a siege following the Mamluk defeat at the Battle of Marj Dabiq.

In 1831, the fortress was depopulated after the Ottoman forces suppressed the rebellion led by the local tax collector. The next year, Egyptian general Ibrahim Pasha bombarded the fortress during the Egyptian–Ottoman War.

The site was historically known as Hromklay, Hromgla, or Klay-Horomakan in Armenian. It was also known as Urumgala by the locals, and the 15th-century traveler Johann Schiltberger recorded it as Urumkala. In Syriac sources, the site was attested to as Šūrō d'Rūmoyē, and by the 11th century, Qal'ah Rūmoytō and Ḥeṣnō d'Rūmoyē. Although the site was known as Rumkale and its variations throughout the entirety of its history from the medieval to late Ottoman period, it was renamed to Qal'at al-Muslimin following its capture by the Mamluk Sultanate in 1292.

Rumkale's strategic location was known to the Assyrian Empire. Rumkale has been suggested to correspond to Shitamrat, which was taken by Shalmaneser III (r. 859 – 824 BC) in 855 BC, due to Rumkale's location on a cliff, which is an uncommon feature among other structures in the region. It is said that John, an apostle of Jesus, lived in Rumkale during Roman times. Although it is possible that the site was fortified by the Roman Empire, no remains of periods earlier than 1000 CE have been identified at the site.

From what remains of the fortress, the foundations may be traced back to the rule by the Byzantine Empire. The structure was potentially guarding the Byzantine frontier and the Roman road following the right bank of the Euphrates. The fortress housed a Syriac Orthodox bishopric during the 5–6th-centuries. Among its bishops were Uranius, who attended the Council of Antioch in 445, Maryiun, who took part in the consecration of Severus of Antioch and was later banished by Justin I (r. 518–27), and John, appointed by Jacob Baradaeus in mid-6th century. The site likely evolved into a settlement in the 11th century with the immigration of Armenians from the north as the Byzantine forces displaced a significant population from their lands.

By the 1080s, the region was under Philaretos Brachamios (r. 1071–1087), a Byzantine-Armenian general who carved up parts of the empire with the defeat at the Battle of Manzikert in 1071. Later, Hromgla became one of Kogh Vasil's domains, who was based in Kaysum to the north, and probably bore allegiance to Philaretos. Despite Kogh Vasil's wish to ally with the Crusader states, his adopted son and successor Vasil Dgha was captured, tortured, and forced to relinquish his lands to Baldwin II of Edessa in 1116. The fortress was likely part of the Lordship of Marash until the downfall of the County of Edessa between 1144 and 1151. The population of Edessa fled to neighboring places following its capture in 1144, including Rumkale. Between about 1147 and 1150, Rumkale served as the prison for Syriac Orthodox Metropolitan Basil bar Shumna, who, after having escaped from Edessa's second capture the previous year, was chained by Joscelin II, Count of Edessa.