Gao /ɡaʊ/ is a city in Mali and the capital of the Gao Region. The city is located on the River Niger, 320 km (200 mi) east-southeast of Timbuktu on the left bank at the junction with the Tilemsi valley.For much of its history Gao was an important commercial centre involved in the trans-Saharan trade. In the 9th century external Arabic writers described Gao as an important regional power and by the end of the 10th century the local ruler was said to be a Muslim.