The British Empire was the largest empire by land area

The British Empire was the largest empire in history by land area, peaking in the early 1920s at roughly 34–35.5 million km² (about 13–13.7 million square miles), or around a quarter of Earth’s land surface.

Two details most summaries blur. First, the peak was not Victorian. The empire reached its maximum only after the First World War, when Britain took over League of Nations mandates carved from defeated Germany’s colonies and the Ottoman Empire, including Palestine and Mesopotamia (modern Iraq). Much of the record-setting map was, in effect, war spoils.

Second, the headline number wobbles. Guinness World Records quotes both over 34 million km² for 1922 and about 35.5 million km² for 1920, because totals shift with what is counted: self-governing dominions such as Canada and Australia, mandates, and thinly held claims.

How it compares

Empire	Peak	Area	Record
British	c. 1920	~35.5M km²	largest overall
Mongol	c. 1279	~24M km²	largest contiguous
Russian	c. 1895	~22.8M km²	second-largest contiguous

Britain’s lands were scattered across oceans; the Mongols held the largest contiguous land empire, one unbroken block of Eurasia. Measured by people rather than acres, the gap narrows: under Kublai Khan the Mongols ruled about 110 million people, roughly a quarter of humanity, while the British Empire of 1940 also held about a quarter of the world’s population. A 2024 book by Rein Taagepera and Miroslav Nemčok, launched at the University of Tartu, treats Britain as the latest in a chain of record-setters running from ancient Egypt through Achaemenid Persia, the Caliphate and the Mongols.

The record was short-lived. The Second World War drained Britain’s resources; India and Pakistan became independent in 1947, and the Imperial War Museums dates the empire’s final end to the 1997 handover of Hong Kong — barely 75 years after the peak.