The Byzantine navy was the naval force of the Byzantine Empire. Like the state it served, it was a direct continuation from its Roman predecessor, but played a far greater role in the defence and survival of the state than its earlier iteration. While the fleets of the Roman Empire faced few great naval threats, operating as a policing force vastly inferior in power and prestige to the army, command of the sea became vital to the very existence of the Byzantine state, which several historians have called a "maritime empire".

Greek fire was an incendiary chemical weapon manufactured in and used by the Eastern Roman Empire from the seventh through the fourteenth centuries. The recipe for Greek fire was a closely-guarded state secret, but historians speculate it may have been made by combining pine resin, naphtha, quicklime, calcium phosphide, sulfur, or niter. Roman sailors would toss grenades loaded with Greek fire onto enemy ships or spray it from tubes. Its ability to burn on water made it an effective and destructive naval incendiary weapon, and rival powers tried unsuccessfully to copy the material.