What did the Romans call the city now known as London?

The Romans called the city now known as London Londinium.

Londinium was established on the River Thames shortly after the Roman conquest of Britain, generally dated to around AD 43–50. Its location made it strategically valuable: the Thames provided a crossing point, while the settlement developed into a major port and road junction linking Roman Britain’s regions.

The name was probably adapted from an older Brittonic place-name, although its exact meaning remains uncertain. It was not necessarily invented by the Romans, and historians debate the precise linguistic route from Londinium to modern London. The city became the capital and commercial center of Roman Britain for much of the Roman period.

A common mix-up is Lundenwic, the later Anglo-Saxon trading settlement near modern Covent Garden. That name belonged to a post-Roman town, not the original Roman city. Roman Londinium stood roughly where the modern City of London is located, and parts of its defensive wall and streets remain archaeologically visible.