A maiden who married Sir Caradoc Briefbras, one of Arthur’s knights, in the First Continuation of Chrétien de Troyes’s Perceval.
Caradoc rescued her from a knight named Alardin, who had abducted her after wounding her brother, Cador. Caradoc married her at Arthur’s court. In a later episode, Caradoc’s evil parents attached a deadly serpent to his arm. Placing Caradoc in a vat filled with vinegar and herself in a vat filled with milk, Guignier caused the snake to unwind itself from the knight and to pursue the sweeter host. As it leapt between them, Cador cleaved off its head, but he accidentally caught part of Guignier’s breast in the stroke. A magic shield provided by Alardin bestowed a golden breast its place.
A chastity test at Arthur’s court, involving a horn, showed that she was the only faithful wife of the Round Table knights. Another source given says her fidelity was shown by a mantle test. A boy brought a mantle to Arthur's court and asserted that it would fit only faithful wives. Various ladies tried it on but it fitted only Guignier.
Guignier is identifiable with the Welsh Tegau Eufron.