Lex Luthor is a fictional character from the television series Smallville. He features from the pilot episode until the season seven finale, and has been played continuously by Michael Rosenbaum, with various actors portraying the character as a child or teen throughout the series. The character of Lex Luthor, first created for comic books by Jerry Siegel and Joe Shuster in 1940 as nemesis of Superman, was adapted to television in 2001 by Alfred Gough and Miles Millar - this is only the third time the character has been adapted to a live action television series. The character has also appeared in various literature based on the Smallville television series, none of which directly continues from or into the television episodes.

Smallville is an American superhero television series developed by writer-producers Alfred Gough and Miles Millar, based on the DC Comics character Superman created by Jerry Siegel and Joe Shuster. The series was produced by Millar/Gough Ink, Tollin/Robbins Productions, DC Comics and Warner Bros. Television. Initially broadcast by the WB, the show premiered on October 16, 2001. After its fifth season, the WB and UPN merged to form The CW, the series' later United States broadcaster until its tenth and final season ended on May 13, 2011.