The following is a list of episodes for
. A total 52 episodes and 1 crossover special were made. Episodes 1 through 10 were intended be season 1 and episodes 11 through 20 were to be season 2 but they were merged into one due to Cartoon Network's schedule.
Ben 10: Ultimate Alien
Season 1: 2010 (Episodes 1 - 20)
April 23, 2010
Ben's secret identity is exposed, casting him into the spotlight. Elsewhere, an alien plans to detonate a nuclear bomb.
April 30, 2010
Ben uses Echo Echo to make two clones of himself to attempt to be in three places at once.
Hit 'Em Where They Live 3
May 7, 2010
Zombozo, Charmcaster, and Vulkanus form an alliance and plan to ambush Ben's parents.
Video Games 4
May 14, 2010
Will Harangue comes up with a mastermind plan to put an end to Ben, the 'menace'.
Escape from Aggregor 5
May 21, 2010
The real story behind Aggregor and his escaped prisoners is revealed.
Too Hot to Handle 6
May 28, 2010
After Kevin accidentally releases Aggregor's third prisoner from a suit that protects others from his radiation, the gang has to stop him from radiating the Earth.
Andreas' Fault 7
June 4, 2010
The gang encounter Argit, who has teamed up with the Forever Knights and Aggregor's fourth prisoner.
June 11, 2010
Ben accidentally gets fused with Aggregor's fifth prisoner who has no plans of getting out of his body...
Hero Time 9
June 18, 2010
Ben's childhood hero makes a comeback while he's on a date with a beautiful, young movie actress.
Ultimate Aggregor 10
October 10, 2010
Aggregor, having recaptured the five aliens, puts his ultimate plan into action.
Map of Infinity 11
October 10, 2010
Ben must stop the newly transformed and extremely dangerous Aggregor from attaining the first piece of the Map of Infinity.
Reflected Glory 12
October 15, 2010
Cash and J.T. take credit for Ben's successes, so Psyphon comes back thinking J.T. and Cash were responsible for Vilgax's defeat.
October 22, 2010
Ben and the gang travel to a water planet in order to stop Aggregor from obtaining the second piece of the Map of Infinity.
Where the Magic Happens 14
October 29, 2010
Gwen is forced to team up with her nemesis, Charmcaster, when the team finds themselves to have to stop Aggregor in a hostile magical dimension.
November 5, 2010
With the fourth piece of the Map of Infinity almost in Aggregor's clutches, the gang chase him through the artificial planetoid known as the Perplexahedron.
The Forge of Creation 16
November 12, 2010
When Aggregor goes after the limitless power of Alien X, the gang are forced to do whatever it takes...
...Nor Iron Bars a Cage 17
November 19, 2010
Old feelings resurface when Kevin returns to the Null Void that housed him for years.
The Enemy of My Enemy 18
December 3, 2010
Argit asks for protection from Ben and Gwen after Kevin decides to finish him off.
Absolute Power: Part 1 19
December 10, 2010
When Ben and Gwen are faced with an unexpected enemy, Gwen turns to Darkstar for help.
Absolute Power: Part 2 20
December 10, 2010
Gwen and Ben have to do whatever it takes to bring down the "mad dog" Kevin.
Season 2: 2011 (Episodes 21 - 32)
The Transmogrification of Eunice 21
February 4, 2011
The gang meet a new girl called Eunice and everything is going well... until Sunder shows up for her.
Eye of the Beholder 22
February 11, 2011
When Baz-El gets captured, it's up to Ben and the others to rescue him.
Viktor: The Spoils 23
February 18, 2011
The team are called in to investigate a dispute in the small country of Zarkovia. Once there, they discover an old enemy is about to be unleashed.
The Big Story 24
March 4, 2011
While looking for a story to put on his site, Jimmy sees a strange meteorite fall to Earth.
Girl Trouble 25
March 11, 2011
Gwen is infuriated by the prospect of her cousin paying the team a visit, and it only gets worse when it is uncovered that her cousin is not entirely human...
Revenge of the Swarm 26
March 18, 2011
The gang face the swarm again, but this time with a new, more powerful queen.
The Creature from Beyond 27
March 25, 2011
An evil creature released from another dimension has plans to enslave the human race for its master.
Basic Training 28
April 1, 2011
Ben, Gwen, and Kevin are forced to go through basic training at the Plumbers' Academy.
It's Not Easy Being Gwen 29
April 8, 2011
A day in the hectic life of Gwen Tennyson.
Ben 10,000 Returns 30
April 15, 2011
Ben 10,000 returns to help Ben battle a new, dangerous threat.
April 22, 2011
Max tells the kids about his first encounter with aliens and the story of how he and Verdona met and fell in love.
Prisoner Number 775 Is Missing 32
April 29, 2011
The team takes a look at the real purpose of Area 51 and have to recapture an escaped alien prisoner.
Season 3: 2011-2012 (Episodes 33 - 52)
The Purge 33
September 16, 2011
Old George brings the Forever Knights in one group in order to vanquish every alien being on Earth.
Simian Says 34
September 23, 2011
A Xenocyte Queen takes over the Arachnichimps' home planet.
Greetings from Techadon 35
September 30, 2011
Ben finds himself in an inescapable situation when Techadons, custom-made to destroy him, start coming after him.
The Flame Keepers' Circle 36
October 7, 2011
Julie joins a fanatical group who, unbeknownst to her, have discovered Vilgax and worship him.
Double or Nothing 37
October 14, 2011
Albedo resurfaces, and he's making money off of Ben's fame.
The Perfect Girlfriend 38
October 21, 2011
The nanochips are back, and have disguised themselves as Julie.
The Ultimate Sacrifice 39
October 28, 2011
The six Ultimate Forms demand their freedom from the Ultimatrix.
The Widening Gyre 40
November 4, 2011
The team battles a new,
dangerous threat in the Pacific Ocean.
The Mother of All Vreedles 41
November 18, 2011
Ma Vreedle plans to create a clone army of her newest spawn, using all of Earth's saltwater as a key ingredient in the cloning process.
A Knight to Remember 42
December 2, 2011
Vilgax and the Flame Keepers' Circle duel George and the Forever Knights, who oppose their goals of reviving Diagon.
Solitary Alignment 43
December 9, 2011
Azmuth reveals how Sir George got his sword and slayed Diagon, and the team decides to make a deal with the First Knight.
Inspector 13 44
February 4, 2012
A mysterious weapon master from Techadon visits Earth and wants the Ultimatrix to enhance his creations.
Enemy of My Frenemy 45
February 11, 2012
Ben, Gwen, and Kevin set out to rescue Charmcaster from Ledgerdomain, but, unbeknownst to them, Charmcaster has plans of her own.
Couples Retreat 46
February 18, 2012
Darkstar finds his way into Ledgerdomain, where he seduces Charmcaster, using her energies in his latest attempt to destroy Ben, Gwen, and Kevin.
Catch a Falling Star 47
February 25, 2012
Movie star Jennifer Nocturne, who is not in her right mind, teams up with the evil Captain Nemesis.
The Eggman Cometh 48
March 3, 2012
Dr. Animo returns with an army of dragon-like mutants, while Ben has his own problems with his new transformation, Jury Rigg.
Night of the Living Nightmare 49
March 10, 2012
Albedo tries to reclaim the Ultimatrix from Ben by transporting him into one of his own worst nightmares.
The Beginning of the End 50
March 17, 2012
The Flame Keepers' Circle try to release Diagon from his dimension, but Vilgax is released instead.
The Ultimate Enemy: Part 1 51
March 24, 2012
Diagon breaks out of the seal and turns all humans into Flame Keepers' Circle soldiers.
The Ultimate Enemy: Part 2 52
March 31, 2012
Vilgax betrays Diagon so that he can absorb all of his power to destroy his one true enemy: Ben Tennyson.