Lugus was an early Celtic god. When the Romans expanded into Celtic territory, Lugus became identified with the Roman god Mercury. Julius Caesar, when writing of the Celtic gods, said that Mercury was the most worshipped god in Gaul.
The name Lugus isn't known directly from any archeological finds, but from inscriptions of the name in other forms — the names of places and other writings refer to different forms of the name generally agreed upon as Lugus. The Roman city of Lugdunum, which is now Lyon in France, means "fort of Lugus". The cities of Lugo in both Spain and Italy likely come from the name Lugus, as do Loudoun, Scotland and Luganom, Switzerland.
Most surviving depictions of Lugus come from the time of Roman occupation in Gaul, where he is usually depicted as a version of Mercury.
Depictions of Lugus also resemble the Germanic god Wotan, or Odin, who was also identified by the Romans as Mercury. It has been suggested that the earlier diety Lugus may have influenced traits of both Wotan and Loki.