Aleppo (; Arabic: ﺣَﻠَﺐ / ALA-LC: Ḥalab, IPA: [ˈħalab]) is a city in Syria, which serves as the capital of the Aleppo Governorate, the most populous governorate of Syria. With an estimated population of 2,098,000 residents as of 2021, it is Syria's second-largest city and also one of the largest cities in the Levant region.

Aleppo is one of the oldest continuously inhabited cities in the world; it may have been inhabited since the sixth millennium BC. Excavations at Tell as-Sawda and Tell al-Ansari, just south of the old city of Aleppo, show that the area was occupied by Amorites by the latter part of the third millennium BC. That is also the time at which Aleppo is first mentioned in cuneiform tablets unearthed in Ebla and Mesopotamia, which speak of it as part of the Amorite state of Yamhad, and note its commercial and military importance. Such a long history is attributed to its strategic location as a trading center between the Mediterranean Sea and Mesopotamia.

For centuries, Aleppo was the largest city in the Syrian region, and the Ottoman Empire's third-largest after Constantinople (now Istanbul) and Cairo. The city's significance in history has been its location at one end of the Silk Road, which passed through Central Asia and Mesopotamia. When the Suez Canal was inaugurated in 1869, much trade was diverted to sea and Aleppo began its slow decline. At the fall of the Ottoman Empire after World War I, Aleppo lost its northern hinterland to modern Turkey, as well as the important Baghdad Railway connecting it to Mosul. In the 1940s it lost its main access to the sea, by Antakya and İskenderun, also to Turkey. The growth in importance of Damascus in the past few decades further exacerbated the situation. This decline may have helped to preserve the old city of Aleppo, its medieval architecture and traditional heritage. It won the title of the Islamic Capital of Culture 2006, and has had a wave of successful restorations of its historic landmarks. The Battle of Aleppo (2012–2016) occurred in the city during the Syrian Civil War, and many parts of the city had suffered massive destruction. Affected parts of the city are currently undergoing reconstruction. An estimated 31,000 people were killed in Aleppo during the conflict.