Ednyfed Fychan (c. 1170 – 1246), full name Ednyfed Fychan ap Cynwrig, was a Welsh warrior who became seneschal to the Kingdom of Gwynedd in Northern Wales, serving Llywelyn the Great and his son Dafydd ap Llywelyn. He was a descendant (9th in descent) of Marchudd ap Cynan, Lord of Rhos, Lord Protector of Rhodri Mawr, King of Gwynedd and an ancestor of Owen Tudor and thereby of the Tudor dynasty, and all its royal successors down to the 21st century and perhaps beyond.
As is usual with medieval orthography, a variety of spellings were used for his name in medieval sources, such as Vychan and Idneved Vachan.Fychan, meaning literally "small" but also "junior" or "younger", is the origin of the common Welsh personal name, Vaughan.
Ednyfed is said to have first come to notice in battle, fighting against the army of Ranulph de Blondeville, 4th Earl of Chester, who attacked Llywelyn at the behest of King John of England. Ednyfed cut off the heads of three English lords in battle and carried them, still bloody, to Llywelyn, who commanded him to change his family coat of arms to display three heads in memory of the feat.
In 1215, he succeeded Gwyn ab Ednywain as seneschal ("distain" in Welsh) of Gwynedd, roughly equivalent to Chief Councillor or Prime Minister. His titles included Lord of Bryn Ffanigl, Lord of Criccieth, and Chief Justice. He was involved in the negotiations leading to the Peace of Worcester in 1218 and represented Llywelyn in a meeting with the king of England in 1232.
Ednyfed had estates at Bryn Ffanigl Isaf near Abergele and at Llandrillo-yn-Rhos, now a suburb of Colwyn Bay. These were the palace of Llys Euryn, on the hill of Bryn Euryn, and Rhos Fynach, on the seashore below it. He also held lands in Llansadwrn and presumably also on Anglesey, where his son had his seat.