The Galactic Commonwealth, also erroneously referred to as the Galactic Republic, the Galactic Empire, the Sith Empire or the Sith Republic, was the sovereign state and ruling government of most of the galaxy from 4622 BBY to 4617 BBY, and large parts of it from 4617 BBY to 4615 BBY.
The Galactic Commonwealth was established in 3622 BBY during the Fall of Coruscant. After Sith Empress Liana Ascalia forced the Galactic Senate to elect her Supreme Chancellor, she declared the Galactic Republic dissolved, despite not having the legal authority to do this. She then declared the Sith Empire dissolved as well, proclaiming the dawn of a new order, the Galactic Commonwealth.
The Commonwealth ruled most of the galaxy relatively undisturbed until 3618 BBY, when various factions united under the banner of the Galactic Liberation Army to topple the rule of the Commonwealth. The GLA waged a galaxywide revolution against the Commonwealth's rule, starting with the Liberation of Alsakan and culminating with the Battle of Kharzem in 3615 BBY. After the fall of Kharzem, the Galactic Commonwealth effectively collapsed, although Darth Sahira took control of what remained of the Commonwealth.