All the articles available in the Celtic mythology section of the Encyclopedia Mythica:
Abandinus; Abarta; Abellio; Abhean; Abnoba; Achall; Achtan; Achtland; Adsullata; Aengus; Aericura; Aes Sidhe; Aeval; Agrona; Ai; Aibell; Aillen; Aimend; Ain; Aine; Airitech; Airmed; Alaunus; Albiorix; Alisanos; Amaethon; Ambisagrus; Anann; Ancamna; Andarta; Andraste; Anextiomarus; Anne, St.; Annwn; Anu; Arawn; Arduinna; Arianrhod; Arnemetia; Artio; Arvernus; Aufaniae; Avalloc; Aveta; Badb; Balor; Banba; Beag; Bebhionn; Belatu-Cadros; Belenus; Belisama; Berecyntia; Bile; Blodeuwedd; Boann; Bodb; Bodb Dearg; Borvo; Bran; Branwen; Branwen; Brea; Breg; Bres; Bride; Brigantia; Brigid; Brigindo; Britannia; Bronach; Bussumarus; Caer; Cailleach; Camma; Camulus; Canola; Carman; Cartimandua; Caswallawn; Cenn Cruaich; Ceridwen; Cernunnos; Cessair; Cethlion; Cliodhna; Clota; Cocidius; Conall Cernach; Conchobar; Condatis; Conn; Contrebis; Corb; Cormac Mac Airt; Coventina; Creiddylad; Creidhne; Crom Cruach; Cu Roi; Cuchulainn; Curoi mac Daire; Cwn Annwn; Cyhiraeth; Dagda; Damara; Damona; Danu; Dea Matrona; Dea Sequana; Dechtere; Deirdre; Dewi; Dia Griene; Dian Cecht; Dis; Don; Dwyn; Dylan; Edain; Elen; Eloi, St.; Emer; Epona; Eri; Eriu; Esus; Etain; Ethne; Fagus; Fand; Ferdiad; Fergus; Fergus mac Roich; Fianna; Finn Mac Cumhail; Fionnuala; Firbolg; Fodla; Fomorians; Gae Bulg; Goibniu; Govannon; Grannus; Gwenn Teir Bronn; Gwydion; Gwynn ap Nudd; Hafgan; Hervé, St.; Hooded Spirits; Icaunus; Inghean Bhuidhe; Lasair; Latiaran; Leucetios; Lia Fail; Llew Llaw Gyffes; Llyr; Lud; Lugh; Lugos; Luxovius; Mabon; Macha; Mag Mell; Mag Tuireadh; Manannan mac Lir; Manawydan; Mannan; Maponos; Math Mathonwy; Matres; Midir; Milesians; Modron; Mog Ruith; Morrigan; Murigen; Nantosuelta; Nantosuetta; Nemausus; Nemetona; Niamh; Nisien and Efnisien; Nodens; Nuada; Oengus Mac Oc; Ogma; Ogmios; Ogyruan; Olwen; Plur na mBan; Pryderi; Pwyll; Rhiannon; Robur; Rosmerta; Rudianos; Sabrina; Samhain; Saone; Scathach; Segomo; Sequanna; Shannon; Sheila-na-gig; Shoney; Sirona; Smertios; Sucellos; Sul; Tailtiu; Taliesin; Tamesis; Taranis; Tarvos Trigaranos; Tethra; Teutates; Tir na n-Og; Tuatha Dé Danann; Twm Shon Catti; Verbeia; Vosegus; Wild Hunt; Yonne.