The largest Empire by area was the British Empire which in 1920 spanned over 26.35% of the world’s land.
The largest Empire by contiguous land was the Mongol Empire that stretched over 17.81% of the world’s land in the 12th century.
But according to the Guinness Book of Records, though the Persian Empire spanned over “only” 4.08% of the world’s land it is the largest Empire by share of the world’s population of all time. It is estimated to have ruled 44% of the world’s population at 480BC. At its peak, these Empire subjects are approximated to number 49.4 million of the world’s 112.4 million.
According to this research, back then, humanity was not yet well spread over the globe and, for instance, the entire Indian subcontinent was home to only one million people. America’s population at that time was roughly half a million.
Bonus Fact 1: as big as the Persian Empire was, it was eventually brought down to its knees and conquered by a small kingdom led by one of the world’s greatest strategists and warlords of all time – Alexander the Macedonian all so known as Alexander the Great.
Bonus Fact 2: click here to find out which empire renamed ancient Israel, Palestine, and why?