It has become an important center for all states established in Anatolia and dominated Anatolia throughout history.
Gaziantep was a frontier city during the Roman Empire. When the Roman Empire was divided into two in BC 395, the region remained within the borders of the Eastern Roman Empire (Byzantine). After the spread of Islam, the region was tried to be dominated by Islamic armies. Gaziantep gained a strategic position by becoming a border city of Byzantine. Byzantine showed great effort so as not to lose the region. The region was sometimes dominated by Arabs and sometimes by Byzantine. Abbasid Caliph Harun Reşid conquered the region in 782 and turned it into an 'Avasım' (border) city.
The region was conquered by Turks in 1067. After this date, Gaziantep and its surroundings were ruled by the Anatolian Seljuk State and the Syrian Seljuks. The crusader armies occupied the region in 1098. Gaziantep was affiliated first to Edessa (Urfa) County and then to Maras Seniorship. The region was taken from The Crusaders in 1150 and started to be ruled by the Anatolian Seljuk State. However, a stability could not be provided in the region. The region became a conflict area for Anatolian Seljuks and Atabegs established in Syria. Later on, the region was invaded by Mongols in 1258. The Mamluk Empire saved Gaziantep from the Mongol invasion in 1260 and added within its borders. Being a border city of the Mamluk Empire, Gaziantep then became a city which was tried to be conquered by Dulkadir Principality. These efforts, started at the end of XIV. century, continued until the Ottoman Empire dominated the region.
Yavuz Sultan Selim (Sultan Selim The Stern), who came to Gaziantep in 1516, made the region a sanjak center affiliated to Arab State. Gaziantep was affiliated to Dulkadir Principality (Maras State) in 1531. This continued until 1830. Tax revenues of Antep Sanjak were allocated to Aleppo State between 1818-1830. In 1830, Antep was made as district center and affiliated to Aleppo State. Although Antep was occupied by the Egyptian Khedive for a short period, it was again affiliated to the Aleppo State under the Ottoman rule. Antep became a sanjak center with an administrative arrangement made in 1908. In 1913, Kilis and Halfeti were affiliated to the Antep Sanjak. After Aleppo was invaded by England in 1918, it became an independent Sanjak.
After the proclamation of the Republic, all sanjaks were revoked and turned into provinces in 1924. In 1926, Halfeti district was turned into a district center and affiliated to Sanliurfa province, while Nizip district was made district and affiliated to Gaziantep. In 1933, Pazarcık district from Kahramanmaras province and Islahiye district, which was a district of Osmaniye province that was then revoked, were affiliated to Gaziantep. After a while, Pazarcık district was again affiliated to Kahramanmaras province.
In 1946, Oguzeli district, and in 1957 Araban and Yavuzeli districts were established and affiliated to Gaziantep.
In 1989, Metropolitan Municipality was established, and Sahinbey and Sehitkamil districts were formed in the city center. In 1991, Karkamis from Nizip District and Nurdagi from Islahiye District became district. In 1995, Elbeyli town of Oguzeli district and its villages were affiliated to Kilis province.
