London's Population in 1666: ~465,000 on the Eve of the Great Fire

In 1666, the year of the Great Fire, London's population was approximately 465,000.

• City of London (the "Square Mile"): ~80,000
• Metropolitan suburbs (Liberties, Westminster, Southwark, etc.): ~385,000

This made London the largest city in Western Europe—and one of the most crowded, with timber-framed houses, narrow lanes, and no sanitation infrastructure. The density fueled the fire's devastation (13,200 houses, 87 churches destroyed). Post-fire rebuilding and later expansion drove rapid growth: 675,000 by 1700, 1 million by 1800.