Greek fire was an incendiary ranged weapon used by the Byzantine Empire/Eastern Roman Empire in the 7th century. Historical accounts and mechanical artifacts indicate that it was a liquid substance typically used in naval battles to ignite enemy ships and would burn on the surface of the water. The exact composition of Greek fire has been lost to time, but was probably based on naphtha (a flammable liquid hydrocarbon mixture related to kerosene) and calcium oxide (or "quicklime").

Comparable to the modern incendiary weapon napalm. Not to be confused with green fire, which is fire that burns green.