Boudica or Boudicca (/ˈbuːdɪkə, boʊˈdɪkə/, from Brythonic *boudi 'victory, win' + *-kā 'having' suffix, i.e. 'Victorious Woman', known in Latin chronicles as Boadicea or Boudicea, and in Welsh as Buddug, pronounced [ˈbɨðɨɡ]) was a queen of the ancient British Iceni tribe, who led a failed uprising against the conquering forces of the Roman Empire in AD 60 or 61. 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, ruled as a nominally independent ally of Rome. He 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. The historian Cassius Dio wrote 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 60/61, Boudica led the Iceni and other British tribes in revolt. They destroyed Camulodunum (modern Colchester), earlier the capital of the Trinovantes, but at that time a colonia for discharged Roman soldiers. Upon hearing of the revolt, the Roman governor Gaius Suetonius Paulinus hurried from the island of Mona (modern Anglesey) to Londinium, the 20-year-old commercial settlement that was the rebels' next target. Unable to defend the settlement, he abandoned it. Boudica's army defeated a detachment of the Legio IX Hispana, and burnt both Londinium and Verulamium. In all, an estimated 70,000–80,000 Romans and Britons were killed by Boudica's followers. Suetonius, meanwhile, regrouped his forces, possibly in the West Midlands, and despite being heavily outnumbered, he decisively defeated the Britons. Boudica died, by suicide or illness, shortly afterwards. The crisis of 60/61 caused Nero to consider withdrawing all his imperial forces from Britain, but Suetonius's victory over Boudica confirmed Roman control of the province.

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.

The Boudican revolt against the Roman Empire is referred to in four works from classical antiquity written by three Roman historians: the Agricola (c. 98) and Annals (c. 110s) by Tacitus; a mention of the uprising by Suetonius in his Lives of the Caesars (121); and the longest account, a detailed description of the revolt contained within Cassius Dio's history of the Empire (c. 202 – c. 235).

Tacitus wrote some years after the rebellion, but his father-in-law Gnaeus Julius Agricola was an eyewitness to the events, having served in Britain as a tribune under Suetonius Paulinus during this period.

Cassius Dio began his history of Rome and its empire about 140 years after Boudica's death. Much is lost and his account of Boudica survives only in the epitome of an 11th-century Byzantine monk, John Xiphilinus. He provides greater and more lurid detail than Tacitus, but in general his details are often fictitious.

Both Tacitus and Dio give an account of battle-speeches given by Boudica, though it is thought that her words were never recorded during her life. Although imaginary, these speeches, designed to provide a comparison for readers of the antagonists' demands and approaches to war, and to portray the Romans as morally superior to their enemy, helped create an image of patriotism that turned Boudica into a legendary figure.