Alexander "Lex" Luthor moved to Smallville from Metropolis in October, 2001. Lex was in Reilly Field in October 1989 when the meteor shower hit, and the effects of the blast caused Lex to lose his hair, and cured him of his asthma. His baldness isolated him from his peers, and Lex grew into a bit of a wild child, almost being expelled from Excelsior Prep, getting kicked out of Metropolis University, being involved in the accidental shooting death of his friend Jude Royce, and other incidents which resulted in Lex having a juvenile record. To end his son's self-destructive phase, his father exiled him to Smallville. When Lex's car went over Loeb bridge, Lex was rescued by local teenager Clark Kent and the two became fast friends despite Clark's father's hatred for Lex's father.

Lex has a tempestuous relationship with his father, Lionel. Lex was very close to his mother, Lillian, who passed away when Lex was in his teens. Lex viewed himself as heir apparent to his father's empire, however he struggled daily not to turn into the kind of man his father is, and be judged by his father's actions. He has made some headway in the town of Smallville in turning around the public's perception of him, by becoming a business partner with Nell Potter in restoring the Talon theatre, and leading an employee-lead buyout that saved the jobs over 2500 employees of the former LuthorCorp Fertlizer Plant #3.

Lex's passions include fast cars, beautiful women, and a complete collection of Warrior Angel comic books. Driven by a need to understand what happened to him in 1989, Lex bankrolled Dr. Hamilton's meteor research, setting Hamilton up at the Cadmus research facilities outside Metropolis. However, Lex pulled the plug on Hamilton's research

Lex is Gabe Sullivan's boss, and the two work closely together at the LexCorp Smallville fertilizer plant. Lex first met Chloe when, having heard Gabe raved about his daughter the reporter, he sought her out at Smallville High school. Finding his way to the Torch office, he was struck by her "Wall of Weird" and she was the one who put him on to local scientist and "meteor freak" Dr. Stephen Hamilton.

Chloe interviewed Lex for the Torch, and was caught in the cross-fire when thieves robbed the mansion's vault. As a result, Chloe was thrown form a third storey window, and suffered a broken arm and minor head trauma. Lex made sure she had the best medical care available, and felt personally responsible for her injury. Although the two have interacted rarely on-screen, their brief meetings sparkled with wit as they engaged in what Lex referred to as "verbal judo."

According to the Smallville press kit, Lex was "born and raised in Metropolis. He's the only son of pesticide "king" Lionel Luthor. Until the summer of his ninth birthday, Lex had always sported a thick mop of red hair. That summer, Lex's mother encouraged Lionel to spend more time with his son. Lionel finally agreed to take Lex on a business trip but their father-son bonding was cut short when a bizarre accident caused Lex to lose all his hair. Although Lionel spent a fortune on specialists over the years, nothing could restore Lex's hair. Lionel was never able to look at Lex the same way again. Riddled with guilt and shame, he lavished Lex with money and gifts. He sent him away to the best boarding schools."