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The ancient king, who died in the early 14th century, ruled the Malian Empire in modern West Africa. His massive wealth is attributed to his control of vast natural resources that helped produce more than half of the global supply of salt and gold at the time. When the devout Muslim made his pilgrimage to the holy city of Mecca, historians said he brought more than 10,000 slaves bearing gold bars and dozens of camels laden with gold dust. The monarch is credited with raising the Djinguereber Mosque in Timbuktu, which still stands.

1. Mansa Musa I - $400 billion

( Bruno Cossa / Grand Tour/Corbis )

The ancient king, who died in the early 14th century, ruled the Malian Empire in modern West Africa. His massive wealth is attributed to his control of vast natural resources that helped produce more than half of the global supply of salt and gold at the time. When the devout Muslim made his pilgrimage to the holy city of Mecca, historians said he brought more than 10,000 slaves bearing gold bars and dozens of camels laden with gold dust. The monarch is credited with raising the Djinguereber Mosque in Timbuktu, which still stands.