Γάννυς or Γαίννυς)[1] was a Roman general who commanded the troops of Elagabalus (officially named Antoninus) against Emperor Macrinus in the Battle of Antioch.

According to Edward Gibbon in his Decline and Fall of the Roman Empire: Antoninus himself, who in the rest of his life never acted like a man, in this important crisis of his fate approved himself a hero, mounted his horse, and, at the head of his rallied troops, charged sword in hand among the thickest enemies; whilst the eunuch[2] Gannys, whose occupation had been confined to female cares and the soft luxury of Asia, displayed the talents of an able and experienced general.

Now in the battle Gannys made haste to occupy the pass in front of the village and drew up his troops in good order for fighting, in spite of the fact that he was utterly without experience in military affairs and had spent his life in luxury.

[4]On the way to Rome, Elagabalus and his entourage spent the winter of 218 in Bithynia at Nicomedia, where Gannys was put to death.

Cassius Dio suggests that Gannys, a virtual "foster-father and guardian" to the new emperor, was killed because he pressured Elagabalus to live "temperately and prudently":