Ten years after the battle at Naboo, the Galactic Republic is threatened by a Separatist movement organized by former Jedi Master Count Dooku. Senator Padmé Amidala comes to Coruscant to vote on a motion to create an army to assist the Jedi against the threat. Narrowly avoiding an assassination attempt upon her arrival, she is placed under the protection of Jedi Master Obi-Wan Kenobi and his apprentice Anakin Skywalker. The pair thwart a second attempt on Padmé's life and subdue the assassin, Zam Wesell, who is killed by her employer, a bounty hunter, before she can reveal his identity. The Jedi Council instructs Obi-Wan to find the bounty hunter, while Anakin is tasked to protect Padmé and escort her back to Naboo, where the two fall in love in spite of the Jedi Code that forbids relationships.
Obi-Wan's search leads him to the mysterious ocean planet of Kamino, where he discovers an army of clones being produced for the Republic in a deceased Jedi's name, with bounty hunter Jango Fett serving as their genetic template. Obi-Wan deduces Jango to be the bounty hunter he is seeking, and after a brief battle, places a homing beacon on Jango's ship, the Slave I. Obi-Wan then follows Jango and his clone son, Boba, to the planet Geonosis. Meanwhile, Anakin is troubled by visions of his mother, Shmi, in pain and decides to return to his homeworld of Tatooine with Padmé to save her. Watto reveals that he sold Shmi to moisture farmer Cliegg Lars, who then freed and married her. Cliegg tells Anakin that she was abducted by Tusken Raiders weeks earlier and is likely dead. Determined to find his mother, Anakin ventures out and finds her at the Tusken campsite, still barely alive. After she dies in his arms, an enraged Anakin massacres the tribe. He later declares to Padmé that he will find a way to prevent the deaths of those he loves.
On Geonosis, Obi-Wan discovers a Separatist gathering led by Count Dooku, who is developing a droid army with Trade Federation Viceroy Nute Gunray and ordered the attempts on Padmé's life. Obi-Wan transmits his findings to the Jedi Council but is subdued by Separatist droids. Dooku meets Obi-Wan in his cell and explains his role in the Confederacy of Independent Systems' formation, while implying that a large portion of the Galactic Senate is under the control of his new master, Darth Sidious. He then invites Obi-Wan to join him and stop Sidious. When Obi-Wan refuses, Dooku claims that Obi-Wan's late master and Dooku's former apprentice Qui-Gon Jinn would have, had he been alive. Meanwhile, Senate Representative Jar Jar Binks proposes a successful vote to grant emergency powers to Chancellor Palpatine, allowing the clone army to be authorized.
Anakin and Padmé head to Geonosis to rescue Obi-Wan, but Anakin loses his lightsaber and they are captured by Jango. Dooku sentences the trio to death, but they are saved by a battalion of clone troopers led by Yoda, Mace Windu, and other Jedi. Windu beheads Jango during the ensuing battle. Obi-Wan and Anakin intercept Dooku, and they engage in a lightsaber duel. Dooku injures Obi-Wan and severs Anakin's right arm, but Yoda intercepts and defends them. Dooku uses the Force to distract Yoda and escapes to Coruscant, where he delivers the plans of a super-weapon to Sidious. As the Jedi acknowledge the beginning of the Clone Wars, Anakin is fitted with a robotic hand and marries Padmé on Naboo, with C-3PO and R2-D2 as the only witnesses.
Ewan McGregor as Obi-Wan Kenobi: A Jedi Knight and mentor to his Padawan learner, Anakin Skywalker, who investigates the assassination attempt of Padmé which led him to discover the makings of a Clone Army. In the 10 years since The Phantom Menace, he has grown wiser and more powerful in the use of the Force.
Natalie Portman as Senator Padmé Amidala: Former Queen of Naboo, who has recently been elected the planet's Senator, and Anakin's love interest.
Hayden Christensen as Anakin Skywalker: A former slave from Tatooine and Obi-Wan's gifted Padawan apprentice who is assigned to protect Padmé with whom he falls in love. He is believed to be the "chosen one" of Jedi prophecy destined "to bring balance to The Force." In the 10 years since The Phantom Menace, he has grown powerful but arrogant, and believes that Obi-Wan is holding him back.
Christopher Lee as Count Dooku / Darth Tyranus: A former Jedi Master and former mentor of Obi-Wan's late master Qui-Gon Jinn, who is now the leader of the Separatist movement as Sidious' new Sith apprentice and a suspect in Obi-Wan's investigation.
Samuel L. Jackson as Mace Windu: A Jedi Master sitting on the Jedi Council who warily watches the Galactic Senate's politics.
Frank Oz as the voice of Yoda: The centuries-old Jedi Grandmaster of an unknown alien species. In addition to leading the Jedi Council, Yoda is the instructor for the young Jedi padawans.
Ian McDiarmid as Supreme Chancellor Palpatine / Darth Sidious: A former Galactic Senator from Naboo and secret Sith Lord, who amasses vast emergency powers as the Chancellor of the Galactic Republic upon the outbreak of the Clone Wars.
Pernilla August as Shmi Skywalker: Anakin's mother and a former slave.
Temuera Morrison as Jango Fett: A bounty hunter who gave his DNA for use by the cloning facilities on Kamino for the creation of the clone army. In addition to his wage, he requested an unaltered clone for himself to take as his son – Boba Fett.
Anthony Daniels as C-3PO: A protocol droid built by Anakin as a child who now serves the Lars family. He later leaves Tatooine to accompany Anakin and Padmé.
Daniels also makes a cameo appearance as Dannl Faytonni: An attendee of the Coruscant Outlander Club who witnesses Anakin and Obi-Wan capturing Zam Wesell
Kenny Baker as R2-D2: Anakin's astromech droid who often accompanies him and Obi-Wan on missions.
Daniel Logan as Boba Fett: Jango Fett's clone and adopted son.
Leeanna Walsman as Zam Wesell : A bounty hunter and partner of Jango Fett, who is given the task of assassinating Padmé. Although her appearance is human, she is actually a Clawdite, who can shapeshift.
Silas Carson as Nute Gunray and Ki-Adi-Mundi: Gunray is the Nemoidian Viceroy of the Trade Federation and one of the leaders of the Separatist movement, who puts a hit on Padmé as revenge for his loss against her people on Naboo in The Phantom Menace. Mundi is a Cerean Jedi Master sitting on the Jedi Council.
Ahmed Best as Delegate Jar Jar Binks: Padmé's loyal Gungan friend whom she appoints Representative of Naboo in the Galactic Senate.
Best also makes a cameo appearance as Achk Med-Beq: An attendee of the Coruscant Outlander Club who witnesses Anakin and Obi-Wan capturing Zam Wesell
Jimmy Smits as Bail Organa : A senator from Alderaan.
Jay Laga'aia as Gregar Typho : Padmé's newly appointed captain of security.
Oliver Ford Davies as Sio Bibble: Governor of Naboo.
Rose Byrne as Dormé: Handmaiden of Padmé.
Jack Thompson as Cliegg Lars: Shmi's husband, Owen's father and Anakin's stepfather.
Joel Edgerton as Owen Lars : Cliegg's son and Anakin's stepbrother.
Bonnie Piesse as Beru Whitesun : Owen's girlfriend.
Andy Secombe as Watto: Anakin and Shmi's former slave owner.
Ronald Falk as Dexter Jettster : Obi-Wan's Besalisk friend who runs a diner on Coruscant and informs him about Kamino.
Alethea McGrath as Jocasta Nu, the librarian at the Jedi Temple who helps Obi-Wan gain information about Kamino.
the second installment of the Star Wars prequel trilogy, the fifth Star Wars film to be produced, and the second film in the "Skywalker saga."