Gao (pronounced /goʊ/) is a city in Mali and the capital of the Gao Region. The city is located on the River Niger, lying 320 km (200 mi) east-southeast of Timbuktu. Situated on the left bank of the river at the junction with the Tilemsi valley, it had a population of 86,633 in 2009.

For much of its history Gao was an important commercial centre involved in the trans-Saharan trade. External Arabic sources state that by the 9th century Gao was already an important regional power, and by the end of the 10th century, the local ruler was a Muslim. Towards the end of the 13th century, Gao lost its independence and became part of the Mali Empire, but in first half of the 15th century, the town regained its independence and with the conquests of Sonni Ali (ruled 1464–1492) Gao became the capital of the Songhai Empire. The Empire collapsed after the Moroccan invasion in 1591 and the invaders chose to make Timbuktu their stronghold. By the time of Heinrich Barth's visit in 1854, Gao had declined to become a impoverished village with 300 huts constructed from matting. By 2009, it had a population of 86633.