Coordinates: 51°45′00″N 0°21′14″W / 51.7500°N 0.3539°W / 51.7500; -0.3539

Verulamium was an ancient town in Roman Britain. It was sited in the southwest of the modern city of St Albans in Hertfordshire, Great Britain. A large portion of the Roman city remains unexcavated, being now park and agricultural land, though much has been built upon (see below). The ancient Watling Street passed through the city.

Before the Romans, the settlement was known as Verulamion (perhaps meaning "[settlement of] Uerulamos [Broad-Hand]" in Brittonic), the capital of the Catuvellauni tribe. It was established by their leader Tasciovanus and in this pre-Roman form, was among the first places in Britain recorded by name.

The Roman settlement was granted the rank of municipium in c. AD 50, meaning its citizens had what were known as 'Latin Rights', a lesser citizenship status than the colonias possessed. It grew to a significant town, and as such received the attentions of Boudica of the Iceni in AD 61, when Verulamium was sacked and burnt: a black ash layer has been recorded by archaeologists, thus confirming the Roman written record. It grew steadily: by the early 3rd century it covered an area of about 125 acres (0.51 km²), behind a deep ditch and wall. It is the location of the martyrdom of the first English martyr saint, St Alban, who was a Roman patrician converted by the priest Amphibalus. This story is recorded by the monks of the abbey of the town, notably Brother Matthew Paris in his Anglo-Norman Vie de Seint Auban.