[1][2] Ben Tennyson (voiced by Tara Strong as a child, Yuri Lowenthal as a teenager, portrayed by Graham Phillips in Race Against Time and Ryan Kelley in Alien Swarm) is the main protagonist of the franchise.
At the start of Ben 10, he is a 10-year-old boy[note 1] from Bellwood who, during his summer vacation, discovers the Omnitrix, a prototype device that attaches to his wrist and allows him to transform into various aliens.
Max Tennyson (voiced by Paul Eiding in the classic continuity, David Kaye in the reboot, Adam Wylie as a child, Jason Marsden as a teenager; portrayed by Lee Majors in Race Against Time and Barry Corbin in Alien Swarm) is Ben and Gwen's paternal grandfather.
Rook Blonko (voiced by Bumper Robinson) is a Revonnahgander Plumber who Max assigns to work with Ben after Gwen and Kevin leave Bellwood for college.
Glitch (voiced by Tara Strong) is a character originating from the reboot continuity and a human-Galvanic Mechamorph hybrid who was created after Ben used Upgrade to enhance the Omnitrix.
Lt. Steel (voiced by Michael Gough in the original series, Yuri Lowenthal in Omniverse) is the leader of SECT, a task force that deals with alien criminals.
He inadvertently helped Vilgax destroy Petropia, causing him immense guilt until the planet is restored in the Ultimate Alien episode "The Secret of Chromastone".
Myaxx (voiced by Vanessa Marshall in the original series, Vyvan Pham in Alien Force) is a Chimera Sui Generis and Azmuth's former assistant.
XLR8 (voiced by Jim Ward in the original series, Yuri Lowenthal in Omniverse, Josh Keaton in the reboot) is a Kineceleran, a raptor-like alien from the planet Kinet.
Stinkfly (voiced by Dee Bradley Baker in the classic continuity, Greg Cipes in the reboot) is a Lepidopterran, an insect-like alien from the planet Lepidopterra.
Wildvine (voiced by Jim Ward in the original series, Dee Bradley Baker in Omniverse, David Hornsby in the reboot) is a Florana, a humanoid plant-based alien from the planet Flors Verdance.
Buzzshock (voiced by Tara Strong in the original series and reboot, Eric Bauza in Omniverse) is a Nosedeenian, a battery-like alien from the Nosideen Quasar.
Arctiguana (voiced by Tom Kane in the original series, Eric Bauza in Omniverse) is a Polar Manzardill, a lizard-like alien from the planet X'Nelli.
Blitzwolfer (voiced by Tara Strong in the original series, Kevin Michael Richardson in Omniverse) is a Loboan, a wolf-like alien from the moon Luna Lobo.
Snare-oh (voiced by Richard Green in the original series, Kevin Michael Richardson in Omniverse) is a Thep Khufan, a mummy-like alien from the planet Anur Khufos.
Frankenstrike (voiced by Michael Dorn in the original series, David Kaye in Omniverse) is a Transylian, a Frankenstein-like alien from the planet Anur Transyl.
Eye Guy (voiced by Dee Bradley Baker in the original series, Paul Eiding in Omniverse) is a Opticoid, a humanoid boneless alien from the planet Sightra.
Rath (voiced by John DiMaggio in the classic continuity, Dee Bradley Baker in the reboot) is an Appoplexian, a tiger-like alien from the planet Appoplexia.
SixSix (voiced by Dee Bradley Baker in the original series, Josh Keaton in the reboot) is a Sotoraggian bounty hunter and SevenSeven's brother.
Kraab (voiced by Billy West in the original series, Jeff Bennett in Alien Force, Dee Bradley Baker in Omniverse, Travis Willingham in the reboot) is a Piscciss Premann cyborg and bounty hunter.
Frightwig (voiced by Cree Summer in the classic continuity, Jessica DiCicco in the reboot) is a member of the Circus Freaks who has prehensile, tentacle-like hair.
Thumbskull (voiced by Jeff Doucette in the original series, David Kaye in Omniverse, John DiMaggio in the reboot) is a member of the Circus Freaks who has superhuman strength and a nail-like horn.
Phil Billings (voiced by Robert Patrick in the original series, Rob Paulsen in Omniverse, John DiMaggio in the reboot) is a corrupt former Plumber and partner of Max.
In between the events of the original series and Omniverse, Khyber and Dr. Psychobos use Phil as a test subject for the Nemetrix, giving him the ability to transform into a Terroranchula hybrid.
Zs'Skayr (voiced by Steve Blum in the original series and Omniverse, Jeff Bennett in Alien Force) is the leader of Anur Phaetos and Ghostfreak's genetic donor.
Eon (portrayed by Christien Anholt in Race Against Time, voiced by Yuri Lowenthal and Sean Donnellan in Ultimate Alien, Judd Nelson in Omniverse) is a time-travelling villain and rival of Professor Paradox.
They are voiced by various actors, including Dee Bradley Baker, Paul Eiding, Robert David Hall, Richard McGonagle, and Kevin Michael Richardson.
They are voiced by various actors, including Dee Bradley Baker, Jeff Bennett, Greg Cipes, Diane Delano, Paul Eiding, Will Friedle, Wallace Langham, and Richard McGonagle.
Milleous (voiced by Kevin Michael Richardson in the classic continuity, Roger Craig Smith in the reboot) is Attea's father and the former leader of the Incurseans.
Carl Nesmith (voiced by Christopher McDonald) is a fraud and glory-hound who poses as the superhero Captain Nemesis and stages crimes to make himself look heroic.