Grannus is a Celtic god worshipped in Gaul; he was sometimes accompanied by a consort, most often Sirona. He was often associated with sacred springs and healing waters and was honored at a number of shrines and temples. He may be associated with the sun as well.

Many of Grannus’ inscriptions refer to him as “Apollo Grannus,” reflecting the interpretatio Romana wherein the Romans often equated non-Roman gods they encountered with their own deities.

Myth
Unknown

Cult
Grannus was worshipped at numerous temples and shrines, where he received votive and dedicatory offerings. Otherwise little is known of the specifics of his cult although during the Roman era it may have been similar to that of other known healing deities of the time.

Additionally, a ten-day festival to Grannus is known to have been held in what is now Limoges, France.

Etymology
A number of different possible origins have been suggested for Grannus’ name, including the Indo-European *gwher- or “hot” which could refer to either the sun or to his presence in hot springs, or the Indo-European *gher- or “to shine.”

Tribal and other associations
While Grannus was worshipped alongside Sirona among the Treveri, he was well beyond that region and was not strictly a tribal deity.

Region
Grannus’ worship was particularly common in north-eastern Gaul, but he was worshipped far and wide, and has been attested as far north as Scotland andas far east as Hungary.

Literary evidence
According to the historian Dio Cassius, in 213 AD the Roman emperor Caracalla sought the aid of Apollo Grannus at his shrine but to no avail.

Archaeological evidence
Branges, France; Limoges, France; Grand, France; Horbourg, France; Aachen, Germany; Alzey, Germany; Baumburg, Germany; Bonn, Germany; Ennetach, Germany; Erp, Germany; Faimingen, Germany; Neuenstadt, Germany; Speyer, Germany; Trier, Germany; Brigetio (Szony), Hungary; Rome, Italy; Arnheim, Netherlands; Bretea, Romania; Musselburgh, Scotland; Astorga, Spain