thumb|300px|[[Albrecht Dürer's rendition of the image of Ogmios which Lucian describes]]
Ogmios (sometimes Ogmius; ) is the name given to a Celtic god of eloquence described in Heracles, a work of the Syrian satirist Lucian.
Lucian's Heracles is a prolalia, that is, a short text which was read aloud before a longer public performance. It describes Lucian's viewing of a strange image of Ogmios in Gaul, wherein the god is depicted as a dark-skinned, aged version of the Greek hero Heracles, with a group of happy devotees tied by bejewelled chains to this god's tongue. Lucian describes a Celt who approaches him and explains these features, informing him that they reflect a native association of Ogmios with eloquence, which, the Celt explains, reaches its highest level in old age. Lucian uses this anecdote to prove to his audience that, in old age, he is still competent to deliver public performances.
The evidence outside of Lucian's text for the god Ogmios is quite limited. No image has been uncovered which comes close to that which Lucian describes. The only further evidence for the god which has been largely accepted are on two curse tablets from Brigantium (in Austria), which invoke Ogmios's name. Most scholars accept the existence of the god Ogmios, but a minority have expressed scepticism.
In medieval Irish mythology, the god Ogma was fabled as the inventor of the early Irish alphabet Ogham. Ogmios has frequently been connected with Ogma, but the nature of this connection has proven difficult to define. An etymology linking Ogmios, Ogma, and Ogham poses unresolved chronological and phonological problems.
Lucian's text was much read in the Renaissance, and "Gallic Hercules" (as Ogmios was known) inspired a number of artistic works, including drawings by Albrecht Dürer and Hans Holbein the Younger.
Etymology
Georges Dottin, Christian-Joseph Guyonvarc'h and have proposed to derive the god's name derives from Greek (, "furrow, path"). Though Lucian tell us that Ogmios is the name of the god "in their native tongue", Guyonvarc'h and Le Roux believe it is possible the name may have been borrowed by Gaulish speakers from Greek in the parts of Gaul where Greek was widely spoken (such as Massalia). Jan de Vries is sceptical of this possibility. The Greek word seems to have had a connotation of leadership, which agrees with the iconography Lucian describes.
Celtic etymologies of the theonym have also been given. The potential existence of a reflex of the god's name in Irish mythology (Ogma, discussed below) has been taken to count in favour of such an etymology. Xavier Delamarre suggests that Ogmios is a reflex (through proto-Celtic) of proto-Indo-European * ("way"), derived from the PIE verbal root * ("to drive"). He associates with theonym with the meaning of "a leader along a path".
Lucian's Heracles
Lucian (125 CE – after 180 CE) was a Syrian satirist and rhetorician who wrote in Ancient Greek. His short work Heracles or Hercules () is a , that is, a short introduction intended to arouse audience interest prior to a longer lecture. It reflects on its author's old age, and his ability to deliver public oratory, concluding with an emphatic affirmation of this ability. On this basis, the text is dated late in Lucian's life, after his return from Egypt in 175 CE.
The passage relevant to Ogmios comes at the beginning, where Lucian delivers an ekphrasis (literary description of a work of art) of an image of Heracles:
Puzzling at this picture, a Celt fluent in Greek, whom Lucian describes as versed in Greek and Celtic lore, interjects with an explanation. The copious quotations from Greek that the Celt adduces have been omitted from the following. It has been suggested that Lucian's narrative may have taken place in the semi-Hellenized south of Gaul, In the 19th and early 20th centuries researchers were unanimous in seeing Lucian's image as an invention. More recent scholarship has been balanced between the two views. Amato suggests he could have learned of this picture from Favorinus. and accept it as authentic, but are sceptical of Lucian's explanation. though Euskirchen is unconvinced the ekphrasis can be read this way. Jaś Elsner, for example, calls the image "effectively a self-portrait of the orator as an old man". No wall paintings with scenes of a non-classical type have survived in Gaul. However, Stephanie Boucher argued the hunch of the former was a product of low quality bronze-work; and Euskirchen has argued that the latter's baldness could have been caused by wear to the pottery.
Egger argued that only gods of the underworld were invoked on curse tablets, and that therefore Ogmios should be interpreted as a chthonic deity. Further to this point, Egger pointed out that Lucian compares Ogmios to Iapetus and Charon, both figures of the Greek underworld. De Vries accepts the possibility that these coins represent a different iconographic variety of Ogmios, known in the north of Gaul.
Evidence for Ogmios from proper names has been proposed, but this evidence is quite limited and late. A 4th-century CE inscription on a vase found in Kent gives the female personal name Ocmia, which was interpreted by Anne Ross as a female form of Ogmios. The Frankish personal name Ogmireectherius, recorded in the 7th century CE, was given a Celtic etymology by Alfred Holder, who thought the first half of the name incorporated the theonym Ogmios, though Christian-Joseph Guyonvarc'h has given a Germanic etymology without reference to the theonym. A relationship between Ogma and Ogmios has been supposed, but scholars have been "hard-pressed to delineate" the relationship between these figures, as James MacKillop has put it.
The etymologies of Ogma and Ogham are uncertain. It is not even certain that their etymologies must be connected. As Bernhard Maier has pointed out, the tradition which connects Ogma to Ogham is late, and may only reflect the superficial similarity of the two words. The proposal to explain Ogma as a reflex of Ogmios may pose phonological difficulties. The development of proto-Celtic "gm" in Irish is not clear. If it developed like "gn", the initial g would be dropped, in which case proto-Celtic would have given rise to Middle Irish * or * rather than . On the other hand, given the state of the evidence, Ranko Matasović entertains the possibility that "g" was preserved before "m" in the transition to Irish. This hypothesis has more recently received the favour of .
In the Renaissance
The reception of Lucian's ekphrasis of Hercules Ogmios in the Renaissance has been described as "astonishingly rich". In France, Gallic Hercules was regarded as a founder of the nation, and associated with the French monarchy. Albrecht Dürer's rendition of Ogmios as Hermes (pictured above) is well known, but there is also a drawing from the School of Raphael, a wall painting in the Escurialense, and a very large number of printed woodcuts.