Republic Sienar Systems was the predecessor to Sienar Fleet Systems and was founded during the days of the Galactic Republic by the Sienar family.
It funded the Allied Tion Historical Society. During the Clone Wars, the company supplied numerous vehicles to the Confederacy of Independent Systems, much to the disdain of the Galactic Senate.
Shortly before Emperor Palpatine took control, the Senate ordered the dissolution of Republic Sienar Systems. The company's holdings were also absorbed by the Republic Navy.
However, the Emperor revived the company as Sienar Fleet Systems and placed it under the control of Raith Sienar. Sienar Fleet Systems would later become one of the most important and prolific Imperial manufacturers.