Experience the adventures of Clark Kent (Tom Welling) before he becomes Superman. Found by Martha (Annette O'Toole) and Johnathan Kent (John Schneider), after a meteor shower, Clark was raised as a normal human being. Upon discovering his unique powers, he realizes that he most now do what he can to protect his new home world.

Main Cast:
* Tom Welling as Clark Kent: A teenager with a growing set of abilities, he regularly battles "meteor freaks" in his effort to fix a disaster he believes is his fault. The series centers around Kent and his relationships and adventures.
* Michael Rosenbaum as Alexander "Lex" Luthor: A billionaire, and product of his father's "personal brand of parenting." Throughout the series his transition from best-friend of Clark to most hated enemy is an ever-expanding plot.
* Kristin Kreuk as Lana Lang: A romantic interest for Clark throughout the series. As the series progresses the relationship between the two is a continuing storyline.
* Allison Mack as Chloe Sullivan: Not originally a character from the comics, she has become an intricate player in the Smallville universe. Her love for investigative journalism often leads her into inquiries about Clark, her best friend, and his mysterious disappearances. She eventually learns Clark's secret in season 4.
* Annette O'Toole as Martha Kent: Clark's loving mother. She learned she would never be able to give birth to a child, and was overjoyed when she and Jonathan found Clark in the meteor shower. Clark considers her his "heart and soul". [17] She currently serves as a state senator in Kansas, filling the seat left vacant when her husband died.
* John Glover as Lionel Luthor: Not originally a character from the comics, he has become a regular in the Smallville universe. Lex's father has had many sides during the series. He has gone from feared enemy to a vessel for Jor-El. Since Season 5, he has protected Clark's secret, but his own son believes he may be hiding his true nature.
* Erica Durance as Lois Lane: Chloe's cousin, she initially arrives to investigate Chloe's supposed death. She first meets Clark in season 4, and immediately the pair struggle to get along. Lois is at first not interested in journalism, but takes part in investigative activities with Chloe.
* John Schneider as Jonathan Kent: Clark's devoted father. He would do anything to protect Clark, including sacrificing himself. Like in the 1978 film, Superman, he passes away from suffering heart failure in season 5, the 100th episode of the series.