The Classis Misenensis ("Fleet of Misenum"), later awarded the honorifics praetoria and Pia Vindex, was the senior fleet of the imperial Roman navy.

The Classis Misenensis was founded by Augustus in 27 BC, when the fleet of Italy, until then based mostly at Ostia, was moved to the new harbour of Portus Julius at Misenum in the Bay of Naples.^[1] It was commanded by a praefectus classis, drawn from the highest levels of the equestrian class, those earning more than 200,000 sesterces a year. Its mission was to control the western part of the Mediterranean Sea and, as the honorific praetoria awarded by Vespasian for its support during the civil war of 69^[2] suggests, the classis Misenensis, together with the Classis Ravennatis, formed the naval counterpart of the Praetorian Guard, a permanent naval force at the emperor's direct disposal.

The Classis Misenensis recruited its crews mostly from the East, especially from Egypt.^[2] Since Rome did not face any naval threat in the Mediterranean, the bulk of the fleet's crews were idle. Some of the sailors were based in Rome itself, initially housed in the barracks of the Praetorian Guard, but later given their own barracks, the Castra Misenatium near the Colosseum.^[1] There they were used to stage mock naval battles (naumachiae), and operated the mechanism that deployed the canvas canopy of the Colosseum.^[3] Among the sailors of this fleet, Nero levied the legio I Classis and used some of its leading officers in the murder of his mother Agrippina the Younger.^[1]

In 192, the Misenum fleet supported Didius Julianus, and then participated in the campaign of Septimius Severus against Pescennius Niger, transporting his legions to the East.^[4] The fleet remained active in the East for the next few decades, where the emergence of the Persian Sassanid Empire posed a new threat. In 258–260, the Classis Misenensis was employed in the suppression of a rebellion in North Africa.^[5]

In 324 the fleet's ships participated in the campaign of Constantine the Great against Licinius and his decisive naval victory in the Battle of the Hellespont. Afterwards, the bulk of the ships were moved to Constantinople, Constantine's new capital.

The following list is based on Werner Eck and Hans Lieb, "Ein Diplom für die Classis Ravennas vom 22. November 206", Zeitschrift für Papyrologie und Epigraphik, 96 (1993), pp. 86–88

The following ship names and types of the classis Misenensis have survived: Archived 2007-11-21 at the Wayback Machine

• 1 hexeres: Ops
• 1 quinquereme: Victoria
• 9 quadriremes: Fides, Vesta, Venus, Minerva, Dacicus, Fortuna, Annona, Libertas, Olivus
• 50 triremes: Concordia, Spes, Mercurius, Iuno, Neptunus, Asclepius, Hercules, Lucifer, Diana, Apollo, Venus, Perseus, Salus, Athenonix, Satyra, Rhenus, Libertas, Tigris, Oceanus, Cupidus, Victoria, Taurus, Augustus, Minerva, Parthicus, Euphrates, Vesta, Aesculapius, Pietas, Fides, Danubius, Ceres, Tibur, Pollux, Mars, Salvia, Triumphus, Aquila, Liber Pater, Nilus, Caper, Sol, Isis, Providentia, Fortuna, Iuppiter, Virtus, Castor
• 11 liburnians: Aquila, Agathopus, Fides, Aesculapius, Iustitia, Virtus, Taurus Ruber, Nereis, Clementia, Armata, Minerva

By 79 this fleet had probably nothing larger than a quadrireme in service,^[6] for Pliny the Elder, commander of the fleet, investigated the eruption of Vesuvius in a quadrireme, presumably his flagship and the largest class of vessel in the fleet.

• Roman navy
• Classiarius