In this list below we have combined: 1 possible candidates of others &/or ours for the original of Arthur; and 2 namesakes of Arthur. (The list is not totally complete yet and there are still quite a number more to add.)
As can be seen from the list it is not overly certain that "Arthur" was not and/or was an historical person or persons. He could be a person or persons though, and almost all of our most-likely candidates for the/an original person or persons of "(King) Arthur" are asterisked.
Whether there was or was not a person "(King) Arthur", no orthodox academic Arthurians can disprove that we have pretty much positively proven the 9 battle sites of "Arthur" of "Nennius"/'HB' certainly match the 9 Saxon Shore sites, the only-most that we could concede is that we can't prove whether the match is only (definitely/indisputably) literary (between the HB & ND/SS) or whether the battles were also actually fought there. Our opinion from the seeming evidence is that the battle of Guinnion of HB / "Badon [(1/I/A)]" of DEB was seemingly fought in ca 538 ad.
Asshur/A(r)thura? Vritra? Rudra? Rustam? Xartus(potis)/R(i)ta/Arta/Urta/Asha? Artha/Art-ha "power (& success), riches/abundance"? Agartha/Agarthi (king in centre of world); Herr-Thor (LA Waddell); Ares/Mars [Arthur/Merlin] (Mintz)? Artemis? Arcas/Arkas? Arcturus (leader of other stars in Bootes)? Ursa Major / Draco (Hitching)? Artio? Andarta? Artinis (Armenian sun god)? bear (Daniel)? the bear (god/cult, Ainu)? Leib-olmai "alder man/bear man/bear god" (Lappish)? (Mercury) Artaios/Artaius (Mercury)?
Garthos (Ctesias)? Ardys/Ardus of Lydia? Arteois/Artaois (Median king)?
bronze age (Hitching/Drou); "the Celts lost their independence to Ursus" (king Belgium, 776 bc); Arthgal(lo)/Art(h)egal (HRB); King Arvira(r)gus of Siluria (& Genuissa, brother of Caractacus the Pendragon, mentioned in historical records as granting Joseph of Arimathea 12 hides of land in Glastonbury, HRB)? Fingal &/or Finn mac Coul/Cool (some Arthurians)? Deoartavo(i)s (Cruithne/Caledonia)? Artharus rig Cruthni? 'Ursi Caledonii'/"Caledonian bears"/"British bears"; Roman gens Artorius; {Lucius Artorius Castus (York/Armorica)? / K Batradz (& Narts, Sarmatian/Alan, Malcor/Littleton, Brynjulfson)?} Lucius Urseius/Matusius/Ursinianus "(the) bear" (Abalava); wreathed Bacchic man (Dover Painted House)? general Ursicinus? Ursus ("bear", killed petronius maximus, 422)? Ursinus (antipope 366)?
Arthur's Oven; St Andrew (saltire cross)? St Ursula (dtr of dianotus); St Martin/Mars [Arthur/Merlin] (me/Mintz)? St Armel/Arthmael/Arthmail (the King) (of Brittany, beauty true good website); Breton/French (CJ Adrien); St Leonard('s (forest) [Loyngarth/Llwynarth]? St Padarn/Paternus (3 solemnities/churches [match our SS sites])?
(Cormac mac) A(i)rt (Ireland); "Famed Arthur of Gwerthrynion"/Guartherniaun/Garthwys/Gwarth Ennian /enniaunYrth/yrth(y)r/Einion (Yrth)/Enniaun Girt?
Count Theodosius the Brown Bear? Aurelius Ursicin(i)us (Hoxne)? St Germanus (429)? Vortigern/"Proud Tyrant"? Vortimer [Amr's tomb?]? Ri(g)othamus/Riotimus ("kingliest/great king/high king", Gaul/Britons, 460/470, Sidonius, Ashe)? Natanleod (ASC)? Cerdic (Karen Han)? "Clovis"? Heliodorus (Damo)? white bear/ursus/house of the bear [Northumbria]?
Dux (Britanniarum) (Brunjulfson)? Count of the Saxon Shore? 12 battles/9 battle sites = Saxon Shore;
Sutton Hoo Man/ship-burial [cenotaph, Camlan] (me, M. Wood?)? * Arthur's Avalon/grave = Reculver (Cross)? * mysterious body of Levitating Altar [Reculver Cross] (Hassel, me)? *
(9 men of) Luthor/Liber son of Art? * (7 servants/men of) the (chief) Porter (Glewlwyd/gleuluid Gavaelvawr/Gauaeluaur "great grasp", 'Pa Gur')? * Gwallawg (Taliesin)? * Gwarddur/Gwarthur ("he was no Arthur", din Eidyn, Aneirin 'Y Gododdin')? * Gwythyr ap Greidiawl? *
King Tuduvallus &/or Ninian's Christian king father? * Muircertach mac Erca/Earc (Irish, Dane Pestano)? * Aurelius Ambrosius / Ambrosius Aurelius [Amr] (Gildas DEB, tv)? * the "progeny" of Ambrosius (Gildas)? * Cuneglas(us) (the charioteer of) the Bear; * Cadwaladr/Cadwallon [2nd Arthur between 633-720]? * Bodwyr (Brynjulfson); * [Urien(s) (Brewyn)?] * Maelgwn? *
'brettisccyning'/"British king" (ASC)? * pre-Augustine christian "Ethelbert" (&/or "Ethelric") (552/568/588, ASC/Ethelwerd)? * Authari (Lombard)? * Rothari (Lombard)? * Arthari (P Diaconus)? * Art(h)us (Sweden, 631- 650, me, [Beorna?]); * Pope Pelagius (60th/63rd pope)? * Pope Martin (74th pope)? *
Arthur_ic_Uibar; Artognou desc of Patern[us] Colus/Col[i] (Avi) Ficit (Tintagel) [3 solemnities/churches of Padarn]; Arthur/Artu(i)r/Art?r/Artúr/Art(h)an mac Coaning/Cona(i)ng/Conall / mac (King) Aeda(i)n/Aeden/Aidan mac Gabra(i)n grandson of Fergus Mor (of Dalriada, 570, Adam Ardrey); Artgal_map_Dumnagual (Strathclyde); Gartnait((h)boc) / Arthnach (Damo)? Domangart/Domingart? Arth(r)wys/Athrwys ap Meurig/Myrig/Mar/Mor / Rex Artorius Fili Mavricius (2nd KA, Gwent); * 2nd Arthur (Madoc, Wales, 562, Wilson)? Art(h)ur/Arthwyr (m)ap (King) Petr[oc]/Pedr/Pierre ap Cincar/Cyngar (K Arthur of Dyfed/Demetia, the 'tyrant of Dyfed' / Deisi Arthur, Harleian, Kam) [3 solemnities/churches of Padarn]; * Arthur/Artu(i)r mac/ap/filio/filius Bico(i)r/Bicair Britone/Pritene/Pretene c620/625; Arthwys of Elmet; k Arthwys of the Pennines? Arthur Penuchel (late 6th century)? Art(h)ur of Manaan; Arthuis/Arthwys ap Masgwid/Mascuid Gloff; Artuir_maic_Retheoir? * Artur mac Bruide? Arthfael ap Einydd; Artur grandfather of Feradach (c 697); Owain_Ddantgwyn/dantwyn/danwyn "Arth/Arthur" (k of Rhos, f of Cuneglas, "bears fort")?
Macarthur; Macarthy; Clan Arthur (Scottish); 'A' at Govan (hidden Glascow website?); 'A' at Buncarrick (not far from Wexford, Wamsley);
"(Magnanimous) Arthur" ~ (Great) Britain? "Arthur (as a) pan-Brittonic (folkloric) hero" (Padel/Green) / "Arthur is portrayed as a figure of pan-Brittonic folklore and mythology" (Green/Padel). "Arthurian country/terra Arturi" (Cornish) "Arthur acted as a defender of the island of Britain" (Padel). "by means of Arthur ... they'll call it Britain again" ('Description of England') "King Arthur is not dead" (Cornish motto); "King Arthur’s grave is not known / an eternal wonder is the grave of Arthur" (Carmarthen) ["Arthur's grave site is a mystery" ('Stanzas of the graves')?]
Arthur of Bradley (& Winifred) (Suffolk/East Anglian ballad of marriage of); Arthur (de) Huelgoat?
Rhodri Mawr (Wales)? Arthuriburgum/Etterby; "King Arthur's Round Table henge" (Cumbria/Cumberland); Arthur a Bland (Robin Hood); Robin son of Art? Artook Khan (Turkish)? traditional claimed grave (& cross) of Arthur at Glastonbury? (prince) Arthur (1) duke of Brittany (nephew of K John of England); Arthur 2 (Brittany); Arthur 3 de Richmont (Brittany); Arthur son of Henry vii;
Art(i)gas (Uruguay)? Arthur Jenny of Woodbridge; [Sartre?] Port Arthur (USA/Australia); Arthur's Pass (NZ) Chester Alan Arthur (USA); Arthur Gobinau; Arthur Shopenhauer, Arthur Balfour (British pm); Arthur Conan Doyle Arthur Desmond Art Linkletter (tv); Arthur C Clarke; prince Arthur (William Patrick Albert) (duke) of Connaught (Canada/RSA); Arthur Meigen (Canada pm); clarence arthur king (USA); Arthur Cotterell (mythology); Arthur/Arturs (popular given name in Brazil/Belgium/Paris/Latvia) [Artem/Artyom/Artsiom/Artioms (pop given name in Kazakhstan/Belarus/Latvia/Moldavia/Moscow/Russia/Ukraine)?] ["Arthur and Martha"?]; Uncle Arthur (character name in NZ TV comedy); Arthur-Robin/Arthur-Alexander (a forum-username/political-pseudonym i've used); Arthurnet list; Adam Ardrey?