Boudica or Boudicca (, known in Latin chronicles as Boadicea or Boudicea, and in Welsh as Buddug (Welsh pronunciation: [bɨðɨɡ]) was the wife of a king of the Iceni tribe of Celtic Britons, who led a failed uprising against the conquering forces of the Roman Empire in AD 60 or 61. According to Roman sources, shortly after the uprising failed, she poisoned herself or died of her wounds, although there is no actual evidence of either fate. She is considered a British national heroine and a symbol of the struggle for justice and independence.

Boudica's husband Prasutagus, with whom she had two daughters whose names are unknown, ruled as a nominally independent ally of Rome, and left his kingdom jointly to his daughters and to the Roman emperor in his will. When he died, his will was ignored, and the kingdom was annexed and his property taken. According to the Roman historian Tacitus, Boudica was flogged and her daughters raped. Cassius Dio explains Boudica's response by saying that previous imperial donations to influential Britons were confiscated and the Roman financier and philosopher Seneca called in the loans he had forced on the reluctant Britons.

In 60 or 61, when the Roman governor Gaius Suetonius Paulinus was campaigning on the island of Mona (modern Anglesey) on the northwest coast of Wales, Boudica led the Iceni, the Trinovantes and other British tribes in revolt. They destroyed Camulodunum (modern Colchester), earlier the capital of the Trinovantes, but at that time a colonia, a settlement for discharged Roman soldiers, as well as the site of a temple to the former Emperor Claudius. Upon hearing of the revolt, Suetonius hurried to Londinium (modern London), the 20-year-old commercial settlement that was the rebels' next target. He lacked sufficient numbers to defend the settlement, and he evacuated and abandoned the town. Boudica led an army of Iceni, Trinovantes and others against a detachment of the Legio IX Hispana, defeating them and burning both Londinium and Verulamium.

An estimated 70,000–80,000 Romans and Britons were killed in the three cities by those following Boudica. Suetonius, meanwhile, regrouped his forces, possibly in the West Midlands, and despite being heavily outnumbered he decisively defeated the Celtic Britons. The crisis caused the Roman emporor Nero to consider withdrawing all his forces from Britain, but Suetonius's victory over Boudica confirmed Roman control of the province. Boudica either killed herself to avoid capture (according to Tacitus), or died of illness (according to Cassius Dio).

Interest in these events was revived in the English Renaissance and led to Boudica's fame in the Victorian era and as a cultural symbol in Britain.