Alexander Joseph "Lex" Luthor, one of the most enduring supervillains in DC Comics, serves as Superman's primary archenemy. Created by Jerry Siegel and Joe Shuster, he first appeared in Action Comics #23 in April 1940. In his earliest Golden Age portrayals, Luthor—initially known simply by his surname and depicted with a full head of red hair—was a megalomaniacal scientist and war profiteer who orchestrated global conflicts and devised elaborate weapons to achieve world domination, establishing him as a foil to Superman's heroism through sheer intellect and ambition.

Luthor's appearance and characterization evolved significantly over time. By 1941, due to an artistic oversight that was later incorporated into canon, he became permanently bald, a visual trait that defined most subsequent depictions. During the Silver Age, he remained a brilliant inventor crafting advanced technology and traps to combat Superman, often driven by personal vendettas. A pivotal transformation occurred in the Post-Crisis era following 1985's Crisis on Infinite Earths, where John Byrne's 1986 miniseries The Man of Steel reimagined Luthor as a ruthless, self-made billionaire industrialist and CEO of LexCorp, emphasizing his manipulative corporate power, political influence, and philosophical disdain for Superman as an extraterrestrial obstacle to human progress.

In modern continuities, including the New 52 and DC Rebirth eras, Luthor continues to embody unchecked human genius corrupted by ego and resentment. Key developments include his successful campaign and election as President of the United States in the early 2000s storyline, during which he wielded executive authority against Superman before eventual exposure and impeachment. Though occasionally portrayed in ambiguous or temporarily heroic roles, such as brief alliances with the Justice League, Luthor's core motivation remains his obsessive rivalry with the Man of Steel, positioning him as a timeless symbol of intellectual hubris.