The New Class Modernization Program represented a standardization initiative undertaken by the New Republic Defense Force. This designation also encompassed starships that were developed as part of the earlier Defender program.
The Rebel Alliance fleet was composed of vessels acquired through diverse methods. In contrast to the Galactic Empire, which relied on standardized, contracted ships, the resource-constrained Rebels obtained their vessels through donations from various sources, captures by numerous rebel cells, outright theft from shipyards, defections from the Empire, black market purchases, acquisitions from junkyards, and supplies from Rebel sympathizers with their own ships. However, the wide array of ships, ship types, eras of manufacture, and designs not originally intended for combat introduced significant maintenance and logistical challenges, straining the fleet's limited resources. Additionally, as the Rebel Alliance's military structure matured, the diversity of ship types hindered training, crew rotation, and officer promotion. With the Rebel Alliance's transformation into the New Republic, the need for a structured military became apparent, leading to the commissioning of a standardized navy.

The New Class program, initiated by the New Republic, primarily aimed to design and construct starships with enhanced standardization in both internal components (such as command consoles) and external features (like hull panels). This initial phase resulted in vessels that were essentially upgraded versions of existing, common ships. These included the Corona-class frigate, Belarus-class medium cruiser, and the Republic-class Star Destroyer. The MC90 Star Cruiser, the first Mon Calamari warship built for the New Republic to a standard design, also incorporated significant standardization. Furthermore, the project yielded two reconnaissance vessels: the droid-operated Ferret-class and the larger, crewed Prowler-class. As these ships were deployed, the New Republic retired older starships, especially those converted from commercial or civilian applications. The New Class designs were informed by Bevel Lemelisk's analysis of the captured Worldcraft.

The Sacheen-class light escort represented the first truly new vessel type of the New Class. Following the success of the Sacheen-class, the Republic Engineering Corporation, which led the program's engineering efforts, utilized the same engine, systems, keel, and hull design to create the Hajen-class fleet tender. This approach of leveraging a common base design for multiple ship types became standard practice for the New Class program. Ultimately, the program employed four base designs with keel lengths of 190 meters, 375 meters, 700 meters, and 1040 meters, each supporting two ship types named after the initial vessel of each type.
The Fifth Battle Group was the first to consist entirely of New Class vessels. Under the leadership of General Etahn A'baht, the Fifth Battle Group demonstrated the capabilities and versatility of the New Class during the New Republic's engagements against the Yevetha in the battles.
The New Class Modernization Program reached completion around 20 ABY.