The Sith are a group of characters in the Star Wars universe. They are the central antagonists. They are an alliance of Force Users who use the dark side of the Force.
The Sith are portrayed in the Star Wars films as individuals willing to use the dark side to gain power at any cost. The Star Wars films establish that they draw upon strong emotions, both negative and positive, as the source of their power, and care only about themselves. This contrasts with the Jedi, who forsake emotional attachment in order to serve others and the galaxy as a whole.
Star Wars creator George Lucas took the name "Sith" from Edgar Rice Burroughs' John Carter of Mars series in which the sith are giant, venomous, hornet-like insects that are difficult to kill. The first use of the word "Sith" is in the Star Wars novelization for Star Wars Episode IV: A New Hope, as a title for Darth Vader, the "Dark Lord of the Sith." The Sith are never formally introduced as such on-screen until The Phantom Menace.