Some know him as Darth Sidious, others simply call him Senator/Emperor Palpatine.
Darth Sidious was a human male Dark Lord of the Sith who served as the last Supreme Chancellor of the Galactic Republic, and was the last reigning Dark Lord of the Sith under Darth Bane's Rule of Two.
Sidious, born as Sheev Palpatine, was trained in the dark side of the Force by Darth Plagueis.