To the outside world, Luthor is a wealthy philantrophist and CEO of LexCorp. However, his company has ties to several criminals and Luthor himself is a founding member of the criminal syndicate known as "The Light".
He is voiced by Mark Rolston.
He is first seen in the episode Targets where he is called in to act as an arbitrator between the two states North- and South Rhelasia who are on the brink of war. The negotiations are taking place at a hotel in Taipei but when Luthor arrives he is almost assassinated by the hired killer Cheshire.
After Cheshire is stopped with help from Red Arrow, Luthor vouches for Red Arrow who has mistakenly captured by the police. Roy is not convinced by this act of nobleness and calls out Luthor. Luthor replies that while he does not claim to be an angel, this time he is on the side of the angels. He then heads inside the hotel. Inside the hotel, Roy talks to Luthor again, revealing that he knows that LexCorp is selling weapons to both Rhelasias and would thus profit from war. Luthor assures Roy that there would be much more profit in investing in a peaceful Rhelasia and implies that he may not have been the target of the assassin at all. Luthor attempts to hire Roy to investigate the assassination attempt. While Roy decides to investigate, he claims that he won't do so for Luthor.
After investigating, Roy returns to Lex to reveal that it is Ra's al Ghul himself who wants Lex dead.
During the peace summit, Cheshire once more attempts to assassinate Luthor and the leaders. Everyone present is saved by Red Arrow and Aquaman who shields the people with an aquatic sphere. The arrival of more League assassins, including Sportsmaster, causes both Rhelasian leaders to retreat to the dais. Luthor remains in the room, watching the fight. When one of the assassins jumps onto the dais, Luthor's assistant Mercy Graves is reveled to be an android who shoots the assassin out of the air. This demonstration of power compared with Luthor saving both their lives convinces the two leaders to sign a peace treaty.
After everything is well and Red Arrow and Aqualad have returned home, Luthor meets with Ra's al Gul. It is made clear that both deviced a scheme which would result in Rhelasia's unification under LexCorps political and economical guideance. Both toast to each other, revealing that they are both part of The Light.
On Thanksgiving, Luthor contacts Superboy and invites him to Washington D.C.. There, he introduces himself and reveals to him that he is the new chairman of the board for Project Cadmus. He tells Superboy that Cadmus has built another super clone. Outraged, Superboy heads to Cadmus but at first cannot find any evidence for the clone. Meanwhile, Luthor watches surveillance footage of Superboy examining the facility. Just as Luthor had anticipated, Superboy eventually finds the new clone and releases him. He is promptly attacked when the clone sees the Superman sigil on his shirt. Luthor seems to be concerned when Superboy is beaten.
Luthor then contacts Superboy once more, revealing to him that when he was created, he was created by kryptonian DNA mixed with human DNA opposed to the new genomorph who is purely krypton. Luthor provides Superboy with devices called 'shields' which supress his human DNA and allows him to use his powers at full capacity. Superboy later finds out that Luthor is the founder of Cadmus Labs.
After Superboy fought the genomorph he angrily confronts Luthor for using him. Luthor had planted a tracker on the shield box to find the missing genomorphs (who had secretly built an underground city in order to be free). Luthor does not deny it and also reveals to Superboy that the human DNA used to create him was Luthor's DNA. Luthor claims to be a better father than Superman ever was to him. He tells Superboy that while Superman sees the world as black and white, Luthor sees it as shades of grey. Superboy angrily offers him back the shields, claiming that he doesn't want them. By using a code phrase, Luthor then shuts down Superboy. When Superboy awakens, it is late night and Luthor is long gone.
After having obtained influence over Young Justice team members Superboy, Miss Martian and Artemis, the Light decides to use them to their advantage. Planning to bring their new assets to Santa Prisca to elaborate their plans, Luthor contacts Superboy.
After Superboy has used up all his shields, Luthor claims he has more and lures Superboy to Santa Prisca. There he reveals that he has not come alone but accompanied by Queen Bee, Sportsmaster, Blockbuster and Bane. Cheshire then arrives with Artemis and Queen Bee calls in Miss Martian. Superboy approaches Luthor, feigning to join them in exchange for more shields. Luthor detects the lie and once more uses the code word on Superboy, forcing him to stand down. Before further actions can be taken, Artemis and Miss Martian turn on the Light and attack Blockbuster and Queen Bee. Luthor is approached by Superboy, revealing that the deactivation code was wiped from his brain by Miss Martian. As most of his men are defeated, Luthor calls in Bane and his soldiers to assist them. Bane's mercenaries are taken out by the rest of the Young Justice League. Luthor attempts to escape with the unconscious Queen Bee but is stopped by Aqualad. He sends Mercy Graves to take care of Aqualad and flees into the jungle. While the rest of heroes and villains fight, Luthor and Queen Bee escape via helicopter.
After the real Roy Harper has been found, having been stored away in a temple in Tibet for eight years, he begins to remember how he was abducted. While investigation Luthor, he had been defeated by some of Luthor's men and remembers nothing afterwards. Thus, after finding out that Luthor had cloned him and that said clone had been living the life of "Roy Harper" for the past eight years, Roy sets out to get revenge on Luthor.
While Luthor is dealing with paperwork for the Light, Roy is standing on the opposite roof. He sees Luthor in his office and fires a missile from his rocket launcher into the building. Both Luthor and his assistant Mercy Graves survive. Immediately after the attack, Luthor enters a secret room inside his office and retrieves a suitcase. While telling his security to kill the assassin on the opposite building, he and Mercy head down to the garage. However, they are confronted by Roy who blows up Lex' car. Although Lex seems polite at first, he swiftly orders Mercy to attack Roy. Mercy manages to disarm Roy and while she and Roy fight their way through the parking lot, Lex talks to Roy. He congratulates him on the arsenal he brought and claims that the strongest weapon an opponent can bring with him is his mind.
After Roy has quite literally disarmed Mercy, Luthor seems concerned. While he attempts to approach Mercy, Roy suddenly attack him from behind. He wraps detonation cord around Lex' arm and holds up the trigger. Roy states that the detonation cord around Lex' arm is the very same detonation cord LexCorp sells illegally. Planning to do the same to Luthor Lex previously did to him, Roy intends to blow off Lex' arm but suddenly realizes that he is surrounded by a host of LexCorp security guards, all aiming their guns at him. Lex smugly asks Roy whether he is ready to sacrifice his own life in order to get revenge on Luthor. When the chief of security asks Luthor whether they should take out Roy, Lex states that he will patiently wait for Roy's decision. Luthor adds that since he found out that Roy was freed, he was expecting for this confrontation to happen and took special precautions. He then throws the suitcase in front of Roy's feet. Roy opens it and is deeply shocked by what is inside. Lex then asks him whether it is vengeance he wants, or satisfaction.
When Oliver Queen and the Roy clone arrive at LexCorp, they find Roy. Roy tells them that he did not kill Luthor and reveals that the suitcase he now holds contains a highly technologically advanced metal-arm.
After the Alien race "The Reach", secretly the partners of the Light, have revealed themselves to Earth in the guise of benefactors, LexCorp and the Reach start working together in order to increase food production in order to stop world hunger. This gains LexCorp and Luthor a massive economical boost. Due to the Justice League and the Young Justice team knowing that the Reach is in league with the Light, they obviously don't trust the Reach and investigate the LexCorp Farms building in Smallville by secretly joining a guided tour.
Meanwhile, Luthor is called in to a conference with the remaining members of The Light. Sportsmaster steps before them and demands retribution for the death of his daughter Artemis by the hands of fellow Light member Black Manta. Luthor offers him a substantial monetary compensation but Sportsmaster reveals that he is out for blood, specifically Black Manta's son Aqualad.
At night, the youngsters return to the facility to find out what is happening at LexCorp Farms. They manage to steal an additive that is being added to the food. Although they are supposed to leave unspotted, Arsenal blows up the lab with explosives. An alarm sounds and Lex and Mercy are alerted to the incident. Using the video feed of his security cameras, Lex sees the Young Justice team in his facility. However, when Mercy wants to call in reinforcements Lex tells her that no additional troops are needed and that Mercy should just sit back and enjoy the show. Seconds later, Black Beetle arrives at the facility and attacks the young heroes.
After Black Beetle has been defeated and the heroes have fled, Luthor and Vandal Savage head to the facility to oversee the damage. They come to the conclusion that the damage is minor and that the most profitable part of their business has remained undiscovered. Back in Luthor's office, Luthor tells Savage that as expected, the Young Justice team took a sample of their additive. Luthor claims that the young team has been quite effective and that one day, they must form a team of youngsters on their own.
Luthor actually forms such a team immediately - recruiting the former captives of the Reach who have gained superpowers by the experiments they were subjected to. After forming the team, Luthor lets them test their powers. He eventually calls the group, talking about the irony of the Reach having created the youngsters who will be their undoing. The teens, who want revenge on the Reach for kidnapping them, state that the Reach did not "create" them, they abducted them and experimented on them. Luthor manipulates the guillible teenagers, claiming to know a way how they can truly hurt the Reach.
He reveals to them a hidden way to infiltrate Warworld, also revealing that nine members of the Young Justice team who previously saved the group are currently captives of the Reach on Warworld. Luthor manipulates the youngsters into heading into Warworld and rescuing the Young Justice team. While the youngsters attack the Reach, Luthor secretly sends Deathstroke to Warworld as well and Deathstroke manages to steal the crystal key that powers Warworld.
After the team successfully returned from Warworld, having gained Arsenal as an ally, Arsenal realizes that Luthor has manipulated the youngsters and sent them as a distraction for Deathstroke. After realizing the truth of his words, the youngsters destroy the device Luthor gave them and cut ties with him.
After Black Beetle has taken over the Reach and sent out several machines to destroy Earth, Lex Luthor provides the Young Justice team with technology to stop Earth's destruction. In additon, it is revealed that the Light planned to betray the Reach from the start and thus, Luthor actually built mechanisms to prevent the Reach from inlfuencing the minds of Earth's citizens.
After the defeat of the Reach, UN secretary Tseng resigns. Luthor is rumored to be his successor.
- This is the fourteenth appearance of the DC supervillain and Superman nemesis Lex Luthor.