The Romulan Star Navy was the primary space forces of the Romulan Guard, the military force of the Romulan Star Empire. Also known as the Grand Fleet or Imperial Fleet, or Galae s'Shiar Rihan (lit. "Romulan Imperial Fleet") in the Rihannsu tongue.
The Romulan Star Navy uses a complex organisational structure for its spaces forces. Its fleets are based around particular groups, such as Command Fleets, Praetorian Fleets, Senatorial fleets, Coalition fleets and others. These fleets are then usually assigned to specific "commands", such as Star Command, Exploration Command, Pacification Command or Occupation Command. These fleets are made up of several avaras or 'centuries' of around a hundred vessels. Avaras are then broken down into command wings of ten to twenty vessels, named after the lead vessel (called a 'wingship') of the wing. (The Dominion War Sourcebook: The Fires of Armageddon)
"Galae", the Romulan word translated as "fleet" in Federation Standard, was noted by Terise Haleakala-LoBrutto to historically refer to the Romulan use of massed air power rather than seagoing ships. (TOS novel: The Romulan Way)
During the Dominion War the Romulan Star Navy contributed around 7,000 vessels split into twenty-five fleets. Fourteen of the fleets were command fleets with the rest mainly senatorial or coalition fleets from factions that supported the declaration of war against the Dominion. Sufficient forces were left in the empire to guard against other threats. (The Dominion War Sourcebook: The Fires of Armageddon)
In Remington continuity, Starfleet and the Star Navy had established an officer exchange program in light of the newly-peaceful relations between the two navies' governments. However, the peace was shaken by the defection of a significant portion of the Star Navy to the Romulan Confederacy. The defectors, along with those who defected from the Tal Shiar, formed the Confederate Fleet.
In 2409, with the revelation of Tal'Shiar culpability in the Hobus supernova and the kidnapping of Empress Sela by the Iconians, the Empire was in civil war for the fourth time in three decades. Praetor Velal tr'Hrienteh, formerly khre'enriov (fleet commander) of the Grand Fleet, managed to secure the support of what remained of the navy by 2410, allowing him to cement a tentative powerbase on Rator III. By this point the service was so short of ships it had begun salvaging and repairing any warbird it could, such as the D'dhael Aish'anh-class IRW Gauntlet, previously a museum ship in the Artaleirh system.
Velal sued for peace with the Republic and brought a small flotilla, the fifteen best ships he could muster, along to the summit on Khitomer under the command of Vice Admiral tr'Haldas, led by his flagship the Scimitar-class IRW Lost Road. The summit was attacked by the Tal'Shiar and the Grand Fleet and Romulan Republican Force contingents fought side-by-side to defend the planet. (Saith Daepahr hrrafv Llaiirevha)