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Abandinus: A Romano-Celtic god of whom is little known, except for an inscription found in Cambridgeshire, England.

Abarta: "Performer of Feats". An Irish/Celtic god, a member of the Tuatha Dé Danann.

Abellio: The Gallic god of apple trees. A local deity of the Garonne valley.

Abhean: An Irish/Celtic god, harper of the Tuatha Dé Danann.

Abnoba: The Gallic river and forest goddess, specifically in the region of the Black Forest. From her name, the name of the English river "Avon" is derived.

Adsullata: A Continental Celtic river goddess.

Aericura: A Romano-Celtic chthonic underworld god.

Agrona: The Celtic goddess of strife and slaughter. The river Aeron in Wales is named after her.

Ai (Aoi Mac Ollamain): The Irish poet god, a member of the Tuatha Dé Danann.

Aibell (Aoibhell): An Irish 'fairy' goddess. Aillen: A malevolent beast from the Otherworld in Irish mythology. Aimend: An Irish sun-goddess.

Alaunus: The Celtic version Apollo, who was venerated in the areas of Mannheim and Salzburg in Germany.

Albiorix: "King of the world". An alternative name of the Gaulish god Teutates, which see.

Alisanos (Alisaunus): The local god of Celtic Gaul, specifically the region of the Cite d'Or. Amaethon: The Welsh god of agriculture, son of the goddess Don. He is directly responsible for the war between the deities of the underworld, led by Arawn, and the Children of Don. In the Battle of the Trees (Battle of Cath Godeau) Amaethon's brother Gwydion transformed trees into warriors with whose help the deities of the underworld were defeated.

Ambisagrus: A Continental Celtic god. The Romans with equated him with Jupiter. Ancamna: A water goddess from Continental Celtic mythology. Andarta: A Gallic warrior and fertility goddess in Celtic France.

Andraste (Andrasta, Adraste): The goddess of war in Celtic Britain. In 61 AD the leader of a rebellion against the Roman occupation, the Queen Boudicca, sacriced captive Roman women to this goddess.

Anextiomarus: A British-Celtic tribal deity.

Anne, St.: In a certain Breton legend, St. Anne was a duchess who was turned out of doors by her cruel husband. She was wafted in an angel-guided vessel to Jerusalem and there gave birth to the Virgin Mary. She brought the Virgin up in ways of piety, and then returned to Breton.

Annwn (Annwfn, Annwyn, Annwyfn): The Welsh (Celtic) nether world, ruled by Arawn. Unlike many other underworlds, Annwn is not a place of eternal torment or punishment, and mortals may visit it. From this place the Wild Hunt rides out.

Anu (Ana): An Irish/Celtic fertility goddess, venerated as the mother of the gods. The center of her cult was the fertile Munster in southeast Ireland. The two rounded hilltops near Killarny are called 'the two breasts of Anu'. Anu is occasionally confused with Danu. Arawn: The Welsh god of the underworld. The god Amaethon stole from him a dog, lapwing and roebuck with led to the Battle of the Trees, in which his forces were defeated. A tale in the Mabinogion relates how he persuaded Pwyll to trade places with him for the span of a year and a day. In this period, Pwyll defeated Arawn's rival for dominion of the underworld Hafgan. Because Pwyll also refrained from sleeping with Arawn's wife, they became close friends.

Arduinna: The Gaulish (Celtic) goddess of the moon, hunting, and forests. She was very popular in the Ardennes, to which she gave her name. She is accompanied by a boar, her sacred animal. The Romans equated her with their Diana.

Arianrhod: Arianrhod ("silver wheel", thus, the moon), is one of the descendants of Don. She had two brothers, Gilfaethwy and Gwydion the sister of Math ap Mathonwy, whose quality was that he required a virgin's lap to place his feet in, unless he was at war. When this virgin was raped, Math asked for a replacement, and Arianrhod volunteered. But when she stepped over his rod, she immediately gave birth to two children: a young boy and a blob. (This is likely because the word morwyn may mean either 'virgin' or 'free young woman', but it also indicates her divine status.) The boychild was named Dylan; he was a sea-being who returned to the waves. The blob was snatched up by Arianrhod's brother Gwydion, who hid it in a chest until it grew into a baby. Arainrhod imposed three geases upon this boy: he would have no name unless she named him, he would bear no arms unless she armed him, and he would have no human woman to wife. Thus, Arianrhod denied him the three essential passages to manhood. Nevertheless, Gwydion raised the nameless boy, and one day Arianrhod spied a young boy killing a wren with a single flung stone. She called out that he was a bright lion with a sure hand, and thus he took that name: Llew Llaw Gyffes. Later, Gwydion faked an alarm, and tricked her into arming the boy.

Arnemetia: The British-Celtic water goddess.

Artio: The continental Celtic goddess of bears and the bear cult. She was found mentioned in inscriptions in the Bern region (Switzerland).

Arvernus: The Gallic god of the Arverni. Aufaniae: Continental Celtic deities. They seem to have been matron-like figures.

Avalloc: Found in Welsh pedigrees as the father of the goddess Modron. His own status is unclear. He is occasionally mentioned as the king of the otherworldly kingdom of Avalon.

Aveta: The Gallic goddess of birth and midwifery