Lucas Dunleavy Luthor is the illegitimate son of Lionel Luthor and Rachel Dunleavy, and brother to Lex Luthor. Thus far, he has only appeared in one episode of the television series Smallville.


Lionel forced Rachel to give him up for adoption. Despite his claim to Rachel that Lucas had died, Lionel located him when he was twelve, and continued to keep up with and remained in contact with him.

However, Lucas was never officially adopted and grew up in instability and poverty in various foster homes. Lex Luthor found an eighteen-year-old Lucas in Edge City after a seven month search. He helped Lucas narrowly escape from some gangsters, after Lucas was discovered to be cheating at a card game.

Lex brought Lucas to LuthorCorp to meet Lionel and to covertly organize a takeover of the company. However, Lucas turned on Lex because Lionel offered Lucas ten million dollars to sign his share away. Thinking he had Lucas under his control, Lionel and Lucas plotted together to take Lex's share of the inheritance and have him thrown out of the Luthor Mansion. However, Lucas realized that that at age eighteen, he was entitled to a much more sizeable inheritance than his father was offering. In addition, Lucas still had bitter feelings about what he saw as his abandonment by Lionel. Through observation, Lucas also realized that Lionel was no longer totally blind. Lucas took control of everything that Lex owned, including the Talon.

When Lucas was found by one of the gangsters, he was saved by Clark Kent. Lex discovered that Lionel set Lucas up and revealed this information to him. When Lucas kidnapped Lex, Clark discovered Lucas' vicious nature and followed him in an attempt to rescue Lex. In a tense confrontation, Lucas threatened to kill Lionel unless Lionel killed Lex. With help from Clark's heat vision, Lionel got the upper hand and shot Lucas instead, but the gun was filled with blanks. The brothers revealed the kidnapping to be staged; they had plotted together to reveal that Lionel was no longer blind and worked together to restore Lex's position in LuthorCorp. Lex had Lucas placed safely away under his protection. His current whereabouts are unknown.


Lucas is characterized as a volatile sociopath, willing to do just about anything to secure his own triumph, wealth, or safety, with no remorse or conscience. While trying to win a pick-up basketball game with Clark and Pete, Lucas intentionally elbowed Clark in the chest (to his injury). He threatened to fire Clark and Lana from the Talon simply because he wanted to. When carrying out the kidnapping plan with Lex, he struck Jonathan Kent unconscious. (This was probably not part of the original plan. Jonathan took Lex in after he was kicked out of the mansion; it is unlikely that Lex would have agreed to harm him.) He was willing to doublecross and deceive both Lionel and Lex for financial security from LuthorCorp. However, it seems that Lex's desperation for family intimacy has allowed him to overlook Lucas' transgressions, in that he decided to protect Lucas in the end.