A woman rides past on a pale horse at an easy walking pace. A man sends his fastest rider after her; the rider gallops and falls behind. The next day a better horse, the same result. On the third day the man goes himself, at full speed, and loses ground. Finally he calls out and asks her to stop.
She stops at once, and points out that he could have asked on the first day, and that it would have been much better for the horse.
That exchange, near the start of the First Branch of the Mabinogi, is the whole of Rhiannon in miniature: she is never actually running away, and the men around her keep choosing force where a question would have worked.
She chooses, and she is not chosen
She has come deliberately, out of the otherworld, to find Pwyll, because she is being married against her will to a man named Gwawl and she has selected an alternative. This is not a woman being won. She arranges the courtship, sets the terms and provides the plan when Pwyll — through a piece of open-handed stupidity — promises Gwawl anything he asks for and is asked for Rhiannon herself.
Her solution is the badger-in-the-bag: a bag that cannot be filled until a nobleman treads it down and declares it full, and a wedding feast at which Gwawl is invited to do so and is then tied inside it and beaten by every guest in turn as a game. It is a cruel piece of comedy and it is entirely her design.
The punishment at the mounting block
Three years pass without an heir, and the nobles of Dyfed press Pwyll to take another wife; he asks for one more year, and a son is born. On the night of his birth the six women set to watch fall asleep, the child is gone by morning, and they save themselves by killing a stag-hound's puppies, smearing the blood on the sleeping Rhiannon's face and hands and putting the bones beside her.
She is not executed. Her penance is worse and much stranger: for seven years she must sit by the horse-block at the gate of the court, tell her story to every arriving stranger, and offer to carry them on her back into the hall. Almost nobody accepts. The image of a queen offering to act as a mount is one of the strongest pieces of evidence that a horse goddess stands somewhere behind this text.
Meanwhile, in another part of Wales, Teyrnon's mare foals every May eve and the foal always disappears. He watches with a sword, severs an enormous clawed arm reaching in through the window — and finds outside not the foal but a human boy, wrapped in silk. The child and a colt grow up together. When his identity is finally recognised and he is restored, Rhiannon says that if it is true, her pryder, her care or anxiety, is gone — and the boy is named Pryderi for it.
The Mabinogi is fond of names arriving that way, but the false-accusation plot itself is an international folktale pattern, found across Europe and beyond. Whether the Welsh redactor is preserving a native myth or fitting a familiar tale-type around a horse goddess is genuinely open.
The Third Branch, and the collars
After Pwyll's death she marries Manawydan, and the Third Branch puts her through a second imprisonment. An enchantment empties Dyfed of every human being except four; a magically appearing court draws Pryderi to a golden bowl that fixes his hands to it and his feet to the floor; Rhiannon follows and is caught the same way; thunder and mist take them both.
When they are recovered we learn what they were doing: Pryderi had been made to wear the door-hammers of a gate around his neck and Rhiannon the collars of asses, after carrying hay. Twice in two branches, this queen is degraded specifically into an animal that carries loads. The pattern is too exact to be accidental.
Rigantona, Epona, and what can honestly be claimed
The name descends from a Brittonic form Rīgantonā, "great queen" or "divine queen", which is a divine-sounding title rather than an ordinary personal name.
The obvious comparison is Epona, the Gaulish horse goddess, who is unusually well attested: hundreds of dedications and reliefs across Gaul, the Rhineland and beyond, showing a woman seated side-saddle on a mare, often with foals, keys, grain or birds, popular with cavalry units and with ordinary people who kept horses. She is the only deity of Celtic origin known to have been given a day in a Roman calendar. That is a real cult with real archaeology.
The Rhiannon–Epona equation is an inference and nothing in any text states it. What supports it: the horse imagery, the birds, the divine-queen name, and the sovereign function. What does not: the complete absence of Epona from Welsh sources, and the twelve or more centuries between the Gaulish dedications and the manuscripts. The comparison is worth making and is not proof. Neither is the parallel with the Irish Macha, forced to race horses while pregnant, though that one is at least within the same medieval period.
The Mabinogi is not "the Mabinogion", and the song is not about her
Two corrections worth making because both are repeated constantly.
The collective title Mabinogion was popularised by Lady Charlotte Guest in the 1840s from what appears to be a scribal slip in one manuscript; the medieval term is mabinogi, and the four tales in which Pryderi appears are properly the Four Branches. The tales survive in the White Book of Rhydderch and the Red Book of Hergest, from the fourteenth and early fifteenth centuries, with composition usually placed in the eleventh or twelfth.
And Fleetwood Mac's "Rhiannon" of 1975, which has done more than any translation to put the name in front of an English-speaking public, was not written about the Welsh material at all. Stevie Nicks took the name from a contemporary novel and learned about the Mabinogi afterwards. The song is a genuine part of the name's modern history and it is not a retelling of anything medieval.
The name itself has since become a common Welsh given name, essentially a twentieth-century revival — name histories follows that separately. For where she sits among the Welsh figures, and why they are kept apart from the Irish ones, see the Celtic family tree.
What are the birds of Rhiannon?
They belong to her by name and never appear in her own branch. The Second Branch has three birds singing over the sea at Harlech, so that seven years pass in what feels like an evening; Culhwch and Olwen lists them among impossible demands and describes them as birds that wake the dead and put the living to sleep. She has an established supernatural attribute recorded only in stories she is not in — which is a strong hint that she was a known figure outside the texts we happen to have.
Is Pryderi the main character of the Four Branches?
He is the only figure present in all four, which is one of the reasons for treating the branches as a single work rather than a collection, and he is killed at the end of the Fourth by Gwydion in single combat. But he is never quite the protagonist: each branch gives its attention to someone else, and he functions more like a thread than a hero. Some scholars have argued the whole cycle was once a biography of Pryderi that has been overwritten.
Why does so much happen on a mound?
Gorsedd Arberth is a specific narrative device: anyone of rank who sits on it will either receive wounds and blows or see a wonder. Rhiannon's arrival is the wonder; the enchantment of Dyfed begins from the same mound in the Third Branch. Mounds in both Welsh and Irish tradition are contact points with the otherworld, and the Welsh version has the useful precision of stating the terms in advance.