Largest Empire in History: The British, the Mongols and How Size Is Measured

Contents9

• The largest empire in history by land area
• Why the rankings disagree
• The British Empire: largest overall
• The Mongol Empire: largest contiguous
• The Russian Empire: largest single state
• The largest empire by share of the world's people
• How the title of largest empire passed over time
• Other ways to measure an empire
• Verdict: the largest empire in history

The largest empire in history depends on how "largest" is measured. By land area, the answer is the British Empire in the 1920s. By continuous territory, it is the Mongol Empire of the 13th century. By share of the world's people, sources disagree. This page ranks the biggest empires on each measure and explains why the numbers vary.

TL;DR: By land, the British Empire was largest, at about 13.7 million square miles in the 1920s, nearly a quarter of the Earth's land. The Mongol Empire, at about 9 million square miles, was the largest contiguous empire. By population share, Guinness names the Achaemenid Persian Empire and History.com names the Qing dynasty.

The largest empire in history by land area

The first two rows are checked against two sources. The rest are the estimates published by the political scientist Rein Taagepera and repeated in most rankings. They rest on one line of research, so they are marked disputed here.

How reliable are the area figures?

Peak areas of historical empires.

Status: Disputed. Estimates, not surveys.

Note: History.com gives the British Empire as 13.7 million square miles in the 1920s and the Mongol Empire as about 9 million square miles at its late-13th-century peak. Most other figures come from Rein Taagepera's studies, begun in 1978. Borders of older empires were often vague.

Claimed lands were counted differently. Some areas were barely controlled. So all such figures are rough.

Sources: History.com, "What Were the Biggest Empires in History"; Live Science, "What was the largest empire in the world".

Why the rankings disagree

Different lists of the largest empires rarely match exactly. Several choices change the order.

• Controlled or claimed land. Some figures count areas the empire claimed on maps but barely governed.
• Peak year. An empire's size can differ a great deal between years only a decade apart.
• Dependencies and allies. Protectorates, vassal states and mandates may or may not be counted.
• Measurement. Older borders were often vague, and modern estimates reconstruct them from maps and texts.

This is why this page treats the British and Mongol figures as checked, and the rest as estimates.

The British Empire: largest overall

By the 1920s the British Empire covered nearly a quarter of the Earth's land. It had taken over German and Ottoman lands as League of Nations mandates. History.com notes that Britain passed the Russian Empire around 1840 and the old Mongol record by the mid-19th century. Its growth and fall are traced on the empire of Great Britain page.

The Mongol Empire: largest contiguous

Genghis Khan founded the Mongol Empire in 1206. Under his successors it spread from Korea to Hungary and from Siberia to the Persian Gulf. Unlike the British Empire, its lands formed one continuous block. It split into separate khanates in the later 13th century, so its peak did not last long.

The Russian Empire: largest single state

The Russian Empire, ruled by the Romanovs, grew steadily over land. It spread from Europe across Siberia to the Pacific, and for a time into Alaska. At its height it was one continuous state rather than a network of colonies. Its territory is mapped on the Russian Empire page.

The largest empire by share of the world's people

Achaemenid or Qing?

Largest empire by share of world population.

Status: Disputed. Sources give different answers.

Note: Live Science reports that Guinness World Records names the Achaemenid Persian Empire in 480 BCE. It is thought to have ruled 44 per cent of the world's people. History.com instead names the Qing dynasty, which ruled about 330 million people around 1800, 37 per cent of humanity. Both rest on estimates of ancient populations, which are uncertain.

Sources: Live Science, "What was the largest empire in the world"; History.com, "What Were the Biggest Empires in History".

How the title of largest empire passed over time

The largest empire of each age changed as new powers rose.

• The ancient Near East: Egypt and Akkad were the great territorial states of the third millennium BCE.
• Persia: the Achaemenid Empire, founded by Cyrus the Great around 550 BCE, stretched from Egypt and Anatolia to the Indus.
• Rome and Han China: in the first and second centuries CE, the two empires ruled at the same time at opposite ends of Eurasia.
• The Islamic caliphates: the Umayyads, in the early 8th century, ruled from Spain to Central Asia.
• The Mongols: in the 13th century they built the largest contiguous empire ever.
• European empires: Spain and Portugal from the 16th century, then Russia over land and Britain by sea in the 19th.

Each step brought new tools of rule, from roads and messengers to fleets and railways, which made larger territories possible.

Other ways to measure an empire

Size is not the only measure. History.com also ranks empires by how long they lasted, naming ancient Egypt for its roughly 3,000 years of dynastic rule. Others point to lasting influence, where the Roman Empire stands out despite its smaller area. At its height under Trajan in 117 CE, Rome held land from Britain to Mesopotamia.

What counts as an empire in the first place is covered on the empire meaning page.

Russia built one of the largest land empires. For how it grew, see our guide to the best books about the Romanovs.

Verdict: the largest empire in history

The largest empire in history by land area was the British Empire, at about 13.7 million square miles in the 1920s. The Mongol Empire was the largest contiguous empire, at about 9 million square miles. On population share, reliable sources disagree between the Achaemenid Empire and the Qing dynasty, so that record is marked disputed. For monarchy and empire in general, see the monarchy hub.

Sources checked for this page

• History.com, "What Were the Biggest Empires in History"
• Live Science, "What was the largest empire in the world"
• Britannica, "8 of the largest empires in history"
• Britannica, "Mongol empire"
• The National Archives, "The Victoria Atlas" (archived 2026)

Questions people also ask

What was the largest empire in history?

By land area, the British Empire, which covered about 13.7 million square miles, nearly a quarter of the Earth's land, in the 1920s.

What was the largest contiguous empire?

The Mongol Empire, which reached about 9 million square miles in the late 13th century and stretched from eastern Europe to the Sea of Japan.

Which empire ruled the largest share of the world's people?

Sources disagree. Guinness World Records names the Achaemenid Persian Empire, at about 44 per cent around 480 BCE; History.com names the Qing dynasty, at about 37 per cent around 1800.

Was the Roman Empire the largest empire?

No. At its height under Trajan in 117 CE it was far smaller than the British, Mongol or Russian empires, though its influence was enormous.

Which empire lasted the longest?

By most counts, ancient Egypt, with about 3,000 years of dynastic rule. Among single states, the Roman Empire in the east lasted until 1453, more than 1,400 years after Augustus.