Sith

In the fictional Star Wars universe, the Sith are a group of warrior priests that follow the "dark" side of The Force. Members of the Sith adopt names that are always preceded by "Darth".

Darth Sidious also known as Palpatine and "The Emperor"
Darth Maul
Darth Tyranus also known as Count Dooku
Darth Vader also known as Anakin Skywalker