Fénius Farsaid (also Phoeniusa, Phenius, Féinius; Farsa, Farsaidh, many variant spellings) is a legendary king of Scythia who shows up in different versions of Irish folklore. He was the son of Bathath who was a son of Magog. According to some traditions, he was the creator of the Ogham alphabet and the Gaelic language.
According to recensions M and A of the Lebor Gabála Érenn, Fénius and his son Nél journeyed to the Tower of Babel (in recension B, it is Rifath Scot son of Gomer instead). Nél, who was trained in many languages, married Scota, daughter of Pharaoh Cingris of Egypt, and their son was Goidel Glas.
In the Lebor Gabála Érenn (11th C), he is said to be one of the 72 chieftains who built Nimrod's Tower of Babel, but travelled to Scythia after the tower collapsed.
According to the Auraicept na n-Éces, Fenius journeyed from Scythia together with Goídel mac Ethéoir, Íar mac Nema and a retinue of 72 scholars. They came to the plain of Shinar to study the confused languages at Nimrod's tower. Finding that they had already been dispersed, Fenius sent his scholars to study them, staying at the tower, coordinating the effort. After ten years, the investigations were complete, and Fenius created in Bérla tóbaide "the selected language", taking the best of each of the confused tongues, which he called Goídelc, Goidelic, after Goídel mac Ethéoir. He also created extensions of Goídelc, called Bérla Féne, after himself, Íarmberla, after Íar mac Nema, and others, and the Beithe-luis-nuin (the Ogham) as a perfected writing system for his languages. The names he gave to the letters were those of his 25 best scholars.
Auraicept claims that Fenius Farsaidh discovered four alphabets, the Hebrew, Greek and Latin ones, and finally the Ogham, and that the Ogham is the most perfected because it was discovered last.