Kublai Khan becomes ruler of the Mongol Empire.

Kublai Khan, also known by his temple name as the Emperor Shizu of Yuan and his regnal name Setsen Khan, was the founder and first emperor of the Mongol-led Yuan dynasty of China. He proclaimed the dynastic name "Great Yuan" in 1271, and ruled Yuan China until his death in 1294.

The Mongol Empire was the largest contiguous empire in history. Originating in present-day Mongolia in East Asia, the empire at its height stretched from the Sea of Japan to Eastern Europe, extending northward into the Arctic; east and southward into the Indian subcontinent, mounting invasions of Southeast Asia, and conquering the Iranian plateau; and reaching westward as far as the Levant and the Carpathian Mountains.

May 5 is the 125th day of the year in the Gregorian calendar; 240 days remain until the end of the year.