The primary vessel of the Viscount-class Star Defender line, the Viscount was manufactured for the New Republic initially, and later for the Galactic Alliance.
The design of the Viscount was conceived in the aftermath of the Black Fleet Crisis, prompted by the New Republic's military recognizing a demand for more formidable dreadnoughts. By the time its construction concluded, twenty-five years after the Battle of Yavin, the New Republic had seized so many Super Star Destroyers that the government debated whether to cease further ship construction.
The Viscount was intended as a design prototype, constructed as a battlecruiser with a length of three kilometers. Subsequent, fully realized vessels were 17 kilometer-long dreadnoughts like the Bounty and the Krakana.
Before the Yuuzhan Vong War, it engaged rogue Imperial elements while the New Republic solidified its authority throughout the galaxy, following the formal end of the Galactic Civil War. As the largest and most powerful warship designed by the Mon Calamari, the Viscount and its sister ships were later invaluable during the Yuuzhan Vong invasion.
Initially positioned at Coruscant, the warship was eventually redeployed to Mon Calamari after the reorganization of the New Republic into the Galactic Alliance.
During the Defense of Mon Calamari, Admiral Traest Kre'fey utilized the Viscount as part of a trio of powerful warships that also included the Super Star Destroyer Guardian and the Mon Calamari Star Cruiser Harbinger. The Viscount's long-range weaponry inflicted significant damage on the Yuuzhan Vong fleet.
The Viscount's initial appearance occurred in The New Jedi Order: Vector Prime, a Del Rey novel authored by R. A. Salvatore and released on October 5th, 1999. Although the 2007 Wizards of the Coast Star Wars Roleplaying Game sourcebook, Starships of the Galaxy, Saga Edition, established the Viscount's class length as seventeen kilometers, 2012's The Essential Guide to Warfare identified the Viscount as a unique three-kilometer prototype. Paul R. Urquhart, a co-author of Warfare, attributed this reference to drawing upon both canonical inconsistencies and fan discussions regarding the Viscount's size, while also illustrating the significant variation within Mon Calamari Star Cruiser classes.