Republic Dark Age

The Republic Dark Age was a time period of the Old Republic during the New Sith Wars. During the Dark Age, the Republic essentially ceased to exist.

The start of the Dark Age was considered to be the crushing Sith victory at the Battle of Mizra in 1,466 BBY, although the Republic had been losing ground in the war since before then. Following the defeat, the economic, social, and political structures of the Republic dissolved.

The Sith conquered all of the Republic's territory, save the Core Worlds. The Senate granted almost all of its authority to the Supreme Chancellor, all of whom were Jedi at that point. The Jedi themselves wielded near-unlimited power. The Republic Navy and Army were disbanded and absorbed into the Jedi's Army of Light.

Presumably, the Dark Age was considered over by the time of the Siths' defeat at the Seventh Battle of Ruusan or the following Ruusan Reformation.