In medieval Irish and Scottish stories, Goídel Glas (Old Irish pronunciation: [ˈɡoːi̯ðʲel ɡlas]; known in Latin as Gaithelus) is considered the creator of the Goidelic languages and the ancestor after whom the Gaels are named. This tradition is found in the 11th-century text Lebor Gabála Érenn. A Scottish version of the story is recorded by John of Fordun, who died in 1384.

Auraicept na n-Éces

In the Early Irish book Auraicept na n-Éces, Goídel Glas is described as a Greek who was one of the two sages in the group of Fénius Farsaid:

Gaedel, the son of Ether, the son of Toe, the son of Baracham, a Greek, was one of the two sages in Fénius’s group. From him, the language called Gaelic was named, because "ealg" means noble, and Gaedel gave it a noble name. Gaedel Glas, the son of Agnon or Aingin, the son of Fénius’s father’s older brother, was also a sage. He claimed this language for Gaedel, the son of Ether. Therefore, "Gaedealg" comes from Gaedel, the son of Ether, and "Gaedil" comes from Gaedel, the son of Agnon or Aingin.

The language of the Irish was created here, along with the Additional Language, the Language Parted among the trees, and the Language of the Poets, which is the fourth. The Common Language, which serves everyone, is the fifth.

Now, Fenius Farsaid, the son of Eugenius, Iar, the son of Nema, and Gaedel, the son of Ether, were the three sages who chose these languages. These languages were created in the city of Eotenam, or Athena.

— Auraicept na n-Éces

Scotichronicon

In the 15th century, a book called Scotichronicon tells the story of Goídel Glas. The text describes Goídel as a prince from Greece whose father, the king, did not allow him to have any power. Feeling upset by this, Goídel gathered soldiers and caused problems and damage across the land. Eventually, his father stopped his actions and sent him away from the kingdom.

After being banished, Goídel traveled to Egypt with his followers. There, he helped a Pharaoh named "Chencres" fight off an attack by the Ethiopians. After winning the battle, Goídel supported the Pharaoh in keeping control over the people of Israel. As a reward, Chencres gave his daughter, Princess Scota, to Goídel in marriage.

During the ceremony when King Alexander III of Scotland was crowned in 1249, a Gaelic poet shared a similar story about Goídel Glas. The poet described the king as a descendant of "Gaidheal Glas, son of Neolius, King of Athens, and his wife Scota, daughter of a Pharaoh."

Lebor Gabála Érenn

The story in the Lebor Gabála Érenn describes the origins of the Gaels as descendants of Fénius Farsaid, one of seventy-two leaders who built the Tower of Babel. In this tale, Goídel Glas is the son of Nel (son of Fénius) and Scota (daughter of an Egyptian pharaoh). Goídel Glas is said to have created the Goidelic language from the seventy-two languages that appeared when people spoke different tongues after the Tower of Babel. His descendants, the Goidels or Gaels, faced many challenges similar to those of the Israelites in the Old Testament. They lived in Egypt during the time of Moses and left during the Exodus. They traveled the world for 440 years before settling in the Iberian Peninsula. There, Goídel’s descendant, Breogán, built a city called Brigantia and constructed a tower from which his son Íth saw Ireland. Brigantia is likely the modern city of Corunna in Galicia (then called Brigantium), and Breogán’s tower is probably inspired by the Tower of Hercules, built by the Romans in Corunna.

A story in the Lebor Gabála describes how Gaidel Glas, son of Nel (or Niul), was healed from a snakebite when Moses prayed and placed his staff on Gaidel’s wound. An earlier part of the text mentions that Gaidel’s arms and clothing were green. Michael O’Clery’s version of the Lebor Gabála notes that the snakebite left a green mark on Gaidel, giving him the nickname "Glas" ("the green"). Geoffrey Keating repeats this story but adds that another explanation for the nickname comes from the Irish word for "lock."

Modern scholars believe this tale was mostly created by medieval Irish Christian writers who wanted to connect the Irish people to events and figures from the Old Testament. The names Goidel Glas, Scota, and Fénius come from the names of the Gaels themselves, not the other way around.

Historia Brittonum

The earliest known version of the story appears in the 9th century text called Historia Brittonum. It tells of a nobleman from Scythia whose name is not recorded. He was forced to leave his kingdom and lived with a large family group in Egypt during the time of the Crossing of the Red Sea. He did not chase the Israelites who had fled, and the Egyptians, afraid of his power after many of their soldiers were killed, exiled him. He traveled with his family group across North Africa, then sailed to Iberia. They settled there and lived for about two thousand years, growing into a large nation, before moving to Ireland and then to Dál Riata.

John of Fordun

A Scottish version of the story about Goídel Glas and Scota was written by John of Fordun. This version is not based on the main Irish account found in the Lebor Gabála. Fordun used information from many different sources, and his version is seen as an effort to combine these different stories into one history.

In Fordun's version, Goídel Glas is called Gaythelos. He is the son of a king from Greece named Neolus or Heolaus. This king was sent into exile in Egypt, where he worked for the Pharaoh and married the Pharaoh's daughter, Scota. Different stories explain why Gaythelos was forced to leave Egypt—some say it was after a revolt following the Pharaoh's death, others say it was because of events involving Moses, or because of fear from the Plagues of Egypt, or due to an invasion by Ethiopians. The result of these events was that Gaythelos and Scota were exiled with Greek and Egyptian nobles. After many years of traveling, they settled in Hispania. In the northwest part of the Iberian Peninsula, they lived in a place called Brigancia, which is now known as A Coruña and was called Brigantium by the Romans.

Some older writers believed Gaythelos was the founder of the Portuguese city of Porto. They said he arrived in the Iberian Peninsula at a harbor he named "Portus Gaythelos." The Romans later called this place "Portus Cale" after the Callaici people. The town eventually became known as Portugal.