Taken from the Star Wars Wiki

Palpatine, also known as Darth Sidious, was a Force-sensitiveHuman male who served as the last Supreme Chancellor of the Galactic Republic and the first Emperor of the Galactic Empire. A Dark Lord of the Sith in the Order of the Sith Lords, recorded by history as the most powerful who had ever lived, his entire life was the culmination of a thousand-year plan to overthrow the Republic and the Jedi Order from within.

Born in 82 BBY on the planet Naboo to the aristocratic House Palpatine, Palpatine discovered the Sith at a young age as a collector of dark side artifacts. In 65 BBY, he met Hego Damask, a Muunbusinessman who was in reality the Sith Lord Darth Plagueis. Under Plagueis's manipulation, Palpatine killed his father and pledged himself to his new Master's dark side teachings as Darth Sidious. Palpatine lived a double life for many years, serving an untarnished career as Naboo's ambassador in the Galactic Senate while learning from his master and training a young Zabrak as the Sith assassinDarth Maul. Plagueis and Sidious, both exceptionally skilled and powerful in the Force, were able to conceal their identities from the Jedi for decades. As Plagueis privately searched for the key to eternal life, Sidious manipulated galactic politics, culminating in the blockadeof Naboo by the Trade Federation. In the wake of the political crisis, the Galactic Senate voted to elect him as Supreme Chancellor, and around the same time, in accordance with Bane's Rule of Two, Sidious murdered Plagueis and usurped the role of Sith Master.

As Chancellor of the Republic and Dark Lord of the Sith, Palpatine orchestrated the outbreak of the devastating Clone Wars ten yearsafter the Naboo Crisis. He himself headed both the Galactic Republic and, secretly, the Confederacy of Independent Systems. The public leader of this splinter faction was former Jedi Master Count Dooku, Sidious' second apprentice as Darth Tyranus in the wake of Maul's presumed death on Naboo. As billions perished in the war, the vast majority of Republic citizens rallied behind Chancellor Palpatine, giving him enough support to amend the Galactic Constitution in the name of security and transfer most of the Senate's executive authority to his own office. In 19 BBY, following Tyranus' demise, Palpatine revealed his identity as Darth Sidious to the Jedi Knight Anakin Skywalker, telling that the dark side teachings that Plagueis had pursued could help Skywalker to save his wife, whom Skywalker had foreseen dying untimely. A failed attempt by the Jedi High Council to arrest Palpatine ensued, and Skywalker pledged himself to Sidious' teachings as Darth Vader. All members of the Jedi Order were accused of treason and betrayed by their clone troopers to the point of virtual extermination. Without the Jedi to oppose him, Palpatine declared himself Emperor of the first Galactic Empire, bringing an end to the Republic that had stood for over 25,000 years.