Elen (known in Welsh tradition as Elen Luyddog (Helen of the Hosts); also known as Saint Helen of Caernarfon) was a late 4th-century founder of churches in Wales who is remembered as a saint. Traditionally, she is said to have been a daughter of the Romano-British ruler Octavius and the wife of Macsen or Magnus Clemens Maximus, Emperor in Britain, Gaul and Spain, who was killed in battle in 388.
Church tradition 
Elen was mother of five, including a boy named Cystennin (or Custennin or Constantine). She lived about sixty years later than Helena of Constantinople, the mother of Constantine the Great, whom she has been confused with in times past. She is patron of Llanelan in West Gower and of the church at Penisa'r-waun near Caernarfon, where her feast day is May 22. Together with her sons, Cystennin and Peblig (Publicus, named in the calendar of the Church in Wales), she is said to have introduced into Wales the Celtic form of monasticism from Gaul. Saint Gregory of Tours and Sulpicius Severus record that Maximus and his wife met Saint Martin of Tours while they were in Gaul.
Literary tradition 
Elen's story is told in The Dream of Macsen Wledig, one of the tales associated with the Mabinogion. Welsh mythology remembers her as the daughter of a chieftain of north Wales named Eudaf or Eudwy, who probably lived somewhere near the Roman base of Segontium, now Caernarfon. She is remembered for having Macsen build roads across her country so that the soldiers could more easily defend it from attackers, thus earning her the name Elen Luyddog (Elen of the Hosts). Since many characters in these tales are thought to be Christianized reflections of older deities (see: Welsh mythology), it has been suggested that Elen reflects (along with Rhiannon, etc.) a tradition of goddesses of sovereignty.
She is said to have ordered the making of Sarn Helen, the great Roman road running from Caernarfon to south Wales via Dolgellau, Pennal and Bremia (Llanddewi Brefi). Though this road bears her name it is considerably older than Elen's accepted time period. Many other Roman roads in Wales bear her name (e.g. Llwybr Elen) and she is thus acknowledged as the patron saint of British roadbuilders and the protectress of travellers.
- (Greek) Ἡ Ἁγία Ἑλένη ἡ Πριγκίπισσα. 22 Μαΐου. ΜΕΓΑΣ ΣΥΝΑΞΑΡΙΣΤΗΣ.
- King Arthur and the Goddess of the Land: The Divine Feminine in the Mabinogion by Caitlin Matthews
- Morris, Lewis; Evans, Daniel Silvan (1878). Celtic Remains. J. Parker. p. 159. LCCN 10-13761. OCLC 12825229. OCLC 34225220. Google Book Search. Retrieved on January 25, 2009. (She is listed as ELEN verch Eudaf.)
- Farmer, David Hugh (1997). The Oxford Dictionary of Saints (4th ed). Oxford [u.a.]: Oxford University Press. ISBN 0-19-280058-2. ISBN 978-0-19-280058-9. LCCN 97-12837 OCLC 36597843 (She is listed as Helen of Caernarvon.)
- Pennick, Nigel (1997). The Celtic Saints: An Illustrated and Authoritative Guide to These Extraordinary Men and Women. New York: Sterling Pub.; London: Thorsons. ISBN 0-7225-3481-7. ISBN 0-8069-9600-5. ISBN 978-0-7225-3481-6. ISBN 978-0-8069-9600-4. LCCN 96-39794. OCLC 35986219. OCLC 36791984. OCLC 59667225.
- Celtnet: Nemeton: Celtic Gods: The Cymric Heroine, Elen Lluyddog (Helen of the Hosts)
- Caer Feddwyd: Elen