Diyarbakır Fortress, also known as the Walls of Diyarbakır, is a historic structure located in the Sur district of Diyarbakır province in Turkey. Comprising two sections, namely the inner fortress and the outer fortress, it is characterized by its main entrances known as the Mountain Gate (Harput Gate), Urfa Gate (Rum Gate), Mardin Gate (Tell Gate), and New Gate (Dicle-Euphrates-Suat Gate). The walls have a history of approximately nine thousand years and are one of the longest and widest defensive walls in the world.

Diyarbakır Fortress was included in the UNESCO World Heritage Temporary List in 2000 and was inscribed as a World Heritage Site in 2015. It is considered the second-longest, widest, and most robust fortification walls in the world after the Great Wall of China. However, the fortress walls sustained damage during the 2023 Kahramanmaraş earthquakes.

Historically, the exact time and by whom the Diyarbakır walls were built are not known, but it is believed that the settlement in the inner fortress was the city's initial settlement site. The walls underwent various interventions since the Roman period, especially being restored during the Roman era in 330-338 and 349 AD.

However, the walls face various challenges today. During the 2015-16 Sur conflicts, the UNESCO Heritage Site of Diyarbakır walls and bastions were damaged, with some sections repaired but others rendered unusable due to security reasons.

Architecturally, the walls are primarily constructed using basalt stone, which is abundant in the region. Different materials such as stone, brick, and mortar were used in walls from different periods. The walls stand at a height of 10-12 meters and have a width of 3-5 meters. With a total of 82 bastions, the bastions of the walls are generally semi-circular or polygonal in shape. One of the most remarkable bastions is the Evli Beden Bastion, distinguished by its rich inscriptions and decorations dating back to the Artuqid period.

Furthermore, the walls have four significant gates: the Mountain Gate, Urfa Gate, New Gate, and Mardin Gate. Each gate has its unique architectural features and historical significance.

Diyarbakır Fortress and its walls possess significant historical and cultural richness, emphasizing the importance of their preservation and restoration efforts.