This is the Darth Maul Costume used in 1999 in Star Wars - Episode 1 - The Phantom Menace. The costume is on display at Disney on loan from the Lucas film Archives.
Darth Maul was played by Ray Park. Ray sported this costume as the apprentice to the evil Sith Lord known as Darth Sidious. Darth Sidious was played by Ian McDiarmid.
Darth Maul was on a quest to take out two Jedi Knights. The target Jedi were Obi-Wan Kenobi, who was played by Ewan McGregor, and Qui-Gon Jinn who was played by Liam Neeson. These two Jedi Knights were amidst their own mission which was to settle the growing hostility brewing on the planet Naboo. The conflict was with the Trade Federation.
Ray Park is a martial artist as well as an actor and wore this costume in the first film of Lucas's prequel trilogy.