Guiderius is a legendary British king according Geoffrey of Monmouth

Geoffrey of Monmouth

Geoffrey of Monmouth was a cleric and one of the major figures in the development of British historiography and the popularity of tales of King Arthur...

's Historia Regum Britanniae

Historia Regum Britanniae

The Historia Regum Britanniae is a pseudohistorical account of British history, written c. 1136 by Geoffrey of Monmouth. It chronicles the lives of the kings of the Britons in a chronological narrative spanning a time of two thousand years, beginning with the Trojans founding the British nation...

(History of the Kings of Britain) and related texts. He can probably be identified as deriving from the historical Togodumnus

Togodumnus

Togodumnus was a historical king of the British Catuvellauni tribe at the time of the Roman conquest. He can probably be identified with the legendary British king Guiderius....

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The eldest son of Cymbeline

Cunobelinus

Cunobeline or Cunobelinus was a historical king in pre-Roman Britain, known from passing mentions by classical historians Suetonius and Dio Cassius, and from his many inscribed coins...

, he succeeds his father to the kingship of Britain. Cymbeline had voluntarily paid tribute to Rome

Ancient Rome

Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

, but Guiderius refused to pay it. The emperor

Roman Emperor

The Roman emperor was the ruler of the Roman State during the imperial period . The Romans had no single term for the office although at any given time, a given title was associated with the emperor...

 Claudius

Claudius

Claudius , was Roman Emperor from 41 to 54. A member of the Julio-Claudian dynasty, he was the son of Drusus and Antonia Minor. He was born at Lugdunum in Gaul and was the first Roman Emperor to be born outside Italy...

 responded by invading

Roman conquest of Britain

The Roman conquest of Britain was a gradual process, beginning effectively in AD 43 under Emperor Claudius, whose general Aulus Plautius served as first governor of Britannia. Great Britain had already frequently been the target of invasions, planned and actual, by forces of the Roman Republic and...

. Claudius and his chief of staff, Lelius Hamo, landed at Portchester

Portchester

Portchester is a locality and suburb 10km northwest of Portsmouth, England. It is part of the borough of Fareham in Hampshire. Once a small village, Portchester is now a busy part of the expanding conurbation between Portsmouth and Southampton, on the A27 main thoroughfare...

, entrenching themselves there while besieging the city. Guiderius conscripted all the men of Britain against Claudius and marched south to meet him in battle. The Britons clashed with the Romans and succeeded so well that the Roman army began retreating to their ships.

Hamo, though, put on British armour and began attacking his own army, urging the Britons to do likewise. Because of this, Hamo was able to get close enough to Guiderius to strike him. Guiderius died then or soon after and was succeeded by his brother Arvirargus

Arvirargus

Arvirargus was a legendary, and possibly historical, British king of the 1st century AD. A shadowy historical Arviragus is known only from a cryptic reference in a satirical poem by Juvenal, in which a giant turbot presented to the Roman emperor Domitian is said to be an omen that "you will...

, who took over as king during the battle.

Guiderius appears as a character in Shakespeare's play Cymbeline

Cymbeline

Cymbeline , also known as Cymbeline, King of Britain or The Tragedy of Cymbeline, is a play by William Shakespeare, based on legends concerning the early Celtic British King Cunobelinus. Although listed as a tragedy in the First Folio, modern critics often classify Cymbeline as a romance...

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