The droungarios of the Fleet (Greek: δρουγγάριος τοῦ πλοΐμου/τῶν πλοΐμων, droungarios tou ploïmou/tōn ploïmōn; after the 11th century δρουγγάριος τοῦ στόλου, droungarios tou stolou), sometimes anglicized as Drungary of the Fleet, was the commander of the Imperial Fleet (βασιλικὸς στόλος, basilikos stolos, or βασιλικὸν πλόϊμον, basilikon ploïmon), the central division of the Byzantine navy stationed at the capital of Constantinople, as opposed to the provincial (thematic) fleets. From the late 11th century, when the Byzantine fleets were amalgamated into a single force under the megas doux, the post, now known as the Grand droungarios of the Fleet (μέγας δρουγγάριος τοῦ στόλου, megas droungarios tou stolou), became the second-in-command of the megas doux and continued in this role until the end of the Byzantine Empire.
In response to the Muslim conquests, some time in the latter half of the 7th century, the bulk of the Byzantine navy was formed into a single command, the great fleet of the Karabisianoi (Greek: Καραβισιάνοι, "the Ships' Men"), commanded, like the land themes that appeared around the same time, by a stratēgos (stratēgos tōn karabōn/karabisianōn, "general of the ships/ships' men"). The Karabisianoi, however, proved inadequate and were replaced in the early 8th century by a more complex system composed of three elements, which, with minor alterations, survived until the 11th century: a central fleet based at Constantinople; a small number of large regional naval commands, either maritime themes, like the Theme of the Cibyrrhaeots, or independent commands under a droungarios, which eventually evolved into the maritime themes of the Aegean Sea and of Samos in the course of the 9th century; and a greater number of local squadrons in the land themes, charged with purely defensive and police tasks and subordinate to the local provincial governors.