Which African empire's ruler Mansa Musa was history's richest man?

Mali, in the fourteenth century, and the richest-ever claim is unquantifiable rather than established - his wealth came from gold and salt in an economy with no comparable accounts, so any dollar figure is an invention. What is documented is more interesting than a number.

His pilgrimage to Mecca in 1324 took a caravan reported at thousands of people and camels carrying gold, and he gave and spent so much passing through Cairo that he depressed the value of gold in Egypt for something like a decade. That is a single individual moving a regional economy by shopping.

It also put Mali on European maps. The 1375 Catalan Atlas shows him seated with a gold nugget and a crown, which is how a West African ruler became a fixture of the European geographical imagination. Under him Timbuktu became a centre of scholarship, with mosques and libraries, and manuscripts from that tradition survived to be smuggled out of the city by librarians in 2012 when jihadist groups occupied it.