The following list of legendary kings of Britain ( or ) derives predominantly from Geoffrey of Monmouth's circa 1136 work Historia Regum Britanniae ("the History of the Kings of Britain"). Geoffrey constructed a largely fictional history for the Britons (ancestors of the Welsh, the Cornish and the Bretons), partly based on the work of earlier medieval historians like Gildas, Nennius and Bede, partly from Welsh genealogies and saints' lives, partly from sources now lost and unidentifiable, and partly from his own imagination (see bibliography). Several of his kings are based on genuine historical figures, but appear in unhistorical narratives. A number of Middle Welsh versions of Geoffrey's Historia exist. All post-date Geoffrey's text, but may give us some insight into any native traditions Geoffrey may have drawn on.

Geoffrey's narrative begins with the exiled Trojan prince Brutus, after whom Britain is supposedly named, a tradition previously recorded in less elaborate form in the 9th century Historia Brittonum. Brutus is a descendant of Aeneas, the legendary Trojan ancestor of the founders of Rome, and his story is evidently related to Roman foundation legends.

The kings before Brutus come from a document purporting to trace the travels of Noah and his offspring in Europe, and once attributed to the Chaldean historian Berossus, but now considered to have been a fabrication by the 15th-century Italian monk Annio da Viterbo, who first published it. Renaissance historians like John Bale and Raphael Holinshed took the list of kings of "Celtica" given by pseudo-Berossus and made them into kings of Britain as well as Gaul. John Milton records these traditions in his History of Britain, although he gives them little credence.

Brutus of Britain (Brutus of Troy)

Historia Brittonum, which is a history of the Celtic Britons written in north Wales in 829–30, claims that the Celtic Britons were descended from Trojans from the ancient city of Troy, who were the first to settle on the island of Britain. It is also claimed in Historia Brittonum, as well as Historia Regum Britanniae by Geoffrey of Monmouth, that the first king of the Britons was Brutus of Troy and that the island of Britain was named after him.Geoffrey of Monmouth, Historia Regum Britanniae 1.3–18, 2.1

Lucius of Britain

Lucius was a legendary 2nd-century king of the Britons traditionally credited with introducing Christianity into Britain. Lucius is first mentioned in a 6th-century version of the Liber Pontificalis, which says that he sent a letter to Pope Eleutherius asking to be made a Christian. The story became widespread after it was repeated in the 8th century by Bede in his Ecclesiastical History of the English People, who added the detail that after Eleutherius granted Lucius' request, the Britons followed their king in conversion and maintained the Christian faith until the Diocletianic Persecution of 303. Later writers expanded the legend, giving accounts of missionary activity under Lucius and attributing to him the foundation of certain churches.

There is no contemporary evidence for a king of this name. In 1904 Adolf von Harnack proposed that there had been a scribal error in Liber Pontificalis with 'Britanio' being written as an erroneous expansion for 'Britio', a citadel of Edessa, present day Şanlıurfa in Turkey. The name of the king of Edessa contemporaneous with Pope Eleutherius was Lucius Aelius Aurelius Abgar VIII.

Des grantz geanz Des grantz geanz ("Of the Great Giants"), a 14th-century Anglo-Norman poem, contains a variant story regarding Albion, the oldest recorded name for Britain, and also contains a slightly different list of kings.For a modern edition see Des Grantz Geanz: An Anglo-Norman Poem, edited by Georgine E. Brereton (Oxford, 1937), a translation can also be found in Myths and Legends of the British Isles, Richard Barber. Boydell, 1999, pp. 3–8.Arthurian Literature XIII, Volume 13, James P. Carley, Felicity Riddy, Boydell & Brewer Ltd, 1995, pp. 45–60. The poem states that a colony of exiled Greek royals led by a queen called Albina first founded Britain but before their settlement "no one dwelt there".Barber, 1999, p. 5. Albina subsequently gave her name first to Britain, which was later renamed Britain after Brutus. The poem also attempts by euhemerism to rationalise the legends of giants; Albina is thus described as being "very tall", but is presented as a human queen, a descendant of a Greek king, not a mythological creature.

The Albina myth is also found in some later manuscripts of Wace's Roman de Brut (1155), attached as a prologue.Carley, 1995, pp. 50 ff.

Scota

Scota, in Scottish mythology, and pseudohistory, is the name given to the mythological daughter of an Egyptian pharaoh to whom the Gaels and Scots traced their ancestry. Scota first appeared in literature from the 11th or 12th century and most modern scholars interpret the legends surrounding her to have emerged to rival Geoffrey of Monmouth's claims that the descendants of Brutus (through Albanactus) founded Scotland.Restoration Scotland, 1660–1690: royalist politics, religion and ideas, Clare Jackson, Boydell Press, 2003, pp. 46–47.W. Matthews, "The Egyptians in Scotland: the Political History of a Myth", Viator 1 (1970), pp. 289–306. However some early Irish sources also refer to the Scota legends and not all scholars regard the legends as fabrications or as political constructions.Myth and Identity in Early Medieval Scotland, EJ Cowan, Scottish Historical Review lxiii, No. 176 (Oct. 1984) pp. 111–135. In the Scottish origin myths, Albanactus had little place and Scottish chroniclers (e.g., John of Fordun and Walter Bower) claimed that Scota was the eponymous founder of Scotland and the Scots long before Albanactus, during the time of Moses.

Monarchs derived from Geoffrey of Monmouth Geoffrey synchronises some of his monarchs with figures and events from the Bible, Greek, Roman and Irish legends, and recorded history. These are given in the "Synchronisation" column of the table below. Geoffrey dated Brutus' arrival in Britain (and subsequent founding of the Trojan-British monarchy) to 1115 BC.Geoffrey of Monmouth, The History of the Kings of Britain, Penguin Classics, "Time Chart", p. 286. Geoffrey's book was later retold by Wace (in French) and Layamon (in Middle English); the final column represents Layamon's version.

KingdomSynchronisationLayamon's BrutEnglandScotlandWalesCornwallOtherBibleBrutus I (24 years)CorineusAeneas Silvius (1112–1081 BC)Eli (12th century BC)=Locrinus (10 years)Albanactus (10 years)Camber (10 years)Gwendolen (65 years)=Gwendolen (15 years)=Maddan (40 years)Aeneas Silvius (1112–1081 BC), Homer (8th/7th century BC)SamuelMadanMempricius (20 years)EurystheusSaul (r. 1049–1010 BC)MembrizEbraucus (40 to 60 years)David (r. 1010–970 BC)EbraucBrutus II Greenshield (12 years)Brutus GreenshieldLeil (25 years)Solomon (r. 971–931 BC)LeilRud Hud Hudibras (39 years)Haggai, Amos, Joel, AzariahRuhudibrasBladud (20 years)Elijah (9th century BC)BladudLeir (60 years)LeirCordelia (5 years)CordoilleMarganus I (north of the Humber) and Cunedagius (south of the Humber) (2 years)Morgan & CunidagiusCunedagius (33 years)Romulus (8th century BC)Isaiah, Hosea (8th century BC)CunidagiusRivalloRiwaldGurgustiusGurgustiusSisillius ISilviusJagoLagoKimarcusMarkGorboducGorbodiagoWar between Ferrex and Porrex IFerreus & PorreusCivil war; Britain divided under five unnamed kingsPinnerStateriusRudaucus ClotenDunvallo MolmutiusDunvallo Molmutius (40 years)Donwallo MolineusBrennius (north of the Humber) and Belinus (south of the Humber)Sack of Rome (387 BC)Belin & BrennesBelinusGurguit BarbtrucPartholónGurguintGuithelinGuncelinMarcia (regent)Sisillius II SilliusKinariusRumarusDaniusDamusMorvidusMorbidusGorbonianusGorbonianArchgalloArgalElidurus (5 years)ElidurArchgallo (restored) (10 years)ArgalElidurus (restored)ElidurPeredurus (north of the Humber) and Ingenius (south of the Humber) (7 years)Peredur, JugenesPeredurusElidurus (restored)ElidurA son of GorbonianusLadorMarganus IIMorganEnniaunus ÆnmaunusIdvalloIwalloRunoRimeGerennusGoroncesCatellusCatulusMillusCoillusPorrex IIPorexCherin=FulgeniusFulgeniusEdadusAldusAndragiusAndrogusUrianusUrrianEliud=CledaucusCledusClotenusDotenGurgintiusGurguiriciusMerianusMerianBledudoCapCapOenusOeinSisillius IIISilliusBeldgabredBlaðgabreastArchmailArkinausEldolÆldolfRedonRedionRedechiusRedærtSamuil Penessil (or Samuil, followed by Penessil) Famul-PenicelPirPirCapoirCaporDigueillusEligilleHeli (40 years)HeliLudLudCassibelanusJulius Caesar's invasions of Britain (55–54 BC)CassibelauneTenvantiusTennanciusCunobelineAugustus (30 BC – 14 AD)Jesus (3 BC – 33 AD)KinbelinGuideriusTogodumnus (d. AD 43) during Claudius's conquest of BritainWiðerArvirargusClaudius (10 BC – AD 54), Vespasian (AD 69–79)Mark the Evangelist, Paul of Tarsus(1st century AD)MariusCoilusLucius (d. AD 156)Pope Eleuterus (174–189)Interregnum; war between Severus and SulgeniusSeptimius Severus (Roman emperor 193–211)GetaPublius Septimius Geta (Roman emperor 209–211)Bassianus (Caracalla)Caracalla (Roman emperor 211–217)CarausiusCarausian Revolt (289–296)AllectusAllectus assassinated Carausius in 293Asclepiodotus (10 years)Asclepiodotus and Constantius Chlorus retook Britain in 296CoelConstantius (11 years)Constantius Chlorus, Roman emperor 293–306Constantine IConstantine I, Roman emperor 306–337OctaviusTrahernOctavius (restored)Maximianus (with Dionotus later as regent)Caradocus, then DionotusMagnus Maximus, Roman usurper-emperor 383–388Gracianus MunicepsInterregnum; end of Roman ruleConstantine IIConstantine III, Roman usurper-emperor 407–411ConstansConstans II, Roman usurper-emperor 409–411VortigernVortimerGermanus of Auxerre (378–448), Battle of Aylesford (455)Aurelius AmbrosiusUther PendragonArthur Battle of Badon (c. AD 500), St. Dubricius (c. AD 465 – c. 550)Constantine IIIAurelius Conanus (2 years)Aurelius Caninus, 6th-century king of Gwent or Powys;Cynan Garwyn (582–610), king of PowysVortiporius (4 years)Vortiporius, 6th-century king of DyfedMalgoMaelgwn Gwynedd, 6th-century king of GwyneddKeredicInterregnum; Saxons occupy EnglandMargaduc (Demetia) and Cadvan (Venedotia)BledericAugustine of Canterbury (arrived in Britain in 597)CadvanCadfan ap Iago, 6th/7th-century king of GwyneddCadwalloCadwallon ap Cadfan, 7th-century king of Gwynedd, d. 634Cadwallader (d. AD 689)Cadwaladr ap Cadwallon, 7th-century king of Gwynedd

After the death of Cadwallader, the kings of the Brythons were reduced to such a small domain that they ceased to be kings of the whole Brythonic-speaking area. Two of his relatives, Yvor and Yni, led the exiles back from Brittany, but were unable to re-establish a united kingship. The Anglo-Saxon invaders ruled the south-eastern part of the island of Great Britain, which would become England, after that point in time under the Bretwaldas and later the kings of England. The heirs to the Celtic-British throne continued through the Welsh kings of Gwynedd until that line was forced to submit itself to the Plantagenets in the 13th century. Princes and lords of Gwynedd ruled until the reign of Dafydd III, who ruled from 1282 to 1283. His death marked the end of the house of Brutus. Owen Tudor, grandfather of Henry VII of England, was a maternal descendant of the kings of Gwynedd; Henry's marriage with Elizabeth of York thus signified the merging of the two royal houses (as well as the feuding houses of York and Lancaster).

Forgeries

Pseudo-Berossus