Revenge of The Sith
Mace makes his final film appearance in Star Wars Episode III: Revenge of the Sith. By this point, he has fought in the Clone Wars for three years, during which time he has come to distrust the Republic's Supreme Chancellor, Palpatine (Ian McDiarmid). When Palpatine appoints Anakin as his personal representative on the Jedi Council, Windu fears that the move is designed to give the Chancellor a vote in Jedi affairs, and casts a key vote in denying Anakin the full rank of Jedi Master.
Shortly afterwards, Anakin tells Mace he has learned that Palpatine is in fact the Sith Lord Darth Sidious. Mace, accompanied by Jedi Masters Kit Fisto, Agen Kolar, and Saesee Tiin, goes to the Chancellor's office to confront him, though the Dark Lord may have actually expected his arrival. Resisting arrest, Palpatine brandishes a red lightsaber and launches himself at the Jedi, killing all three of Mace's companions and engaging him in a lightsaber duel. Windu gains the upper hand in winning the lightsaber part of the entire duel and disarms the Sith Lord, who fires Force lightning at him; Windu blocks the lightning with his lightsaber and directs it back at Palpatine, scarring the Sith Lord's face. Anakin then arrives and Palpatine begs for help, stating that only he can save Anakin's wife, Padmé Amidala (Natalie Portman). Anakin pleads with Mace not to kill the Chancellor, and that he should stand trial before the Senate. Windu replies that Palpatine controls both the Senate and the courts, and is too dangerous to be kept alive. As Mace prepares to strike, Anakin intervenes and severs Windu's lightsaber hand. Palpatine then casts off his illusion of weakness, and hits Mace with another torrent of lightning, sending Mace plunging out of the chamber window to his death.
Read more about this topic: Mace Windu, Appearances in The Star Wars Films