With Action Comics No. 23 (cover-dated April 1940), Superman creators Jerry Siegel and Joe Shuster introduced the antagonist who still defines the series: Lex Luthor. Unlike most threats Superman had faced so far, Luthor is neither alien nor monster — but a highly intelligent human.
A genius as foe
In his first appearance Luthor acts as a scientific mastermind who stirs up wars from the shadows to profit from chaos and gain power. Notably, early Luthor still had red hair — the later iconic bald look took hold over the 1940s and became his trademark.
Why a man without powers is so dangerous
Precisely because Lex Luthor has no superpowers, he works as the perfect foil to Superman. He stands for human ambition, hubris and the belief that intellect beats raw strength. That conflict — the best of humanity against the supposed best in one man — still gives the rivalry its lasting tension. In modern stories Luthor is sometimes ruthless industrialist, sometimes politician, sometimes brilliant inventor, but always the human who comes closest to Superman.
An early cornerstone of the series
With Lex Luthor the foundation of the Superman cosmos was set early: a hero from Krypton, a brave reporter (Lois Lane, present since No. 1) and a human arch-enemy. Later key figures such as Brainiac (1958) and Supergirl (1959) built on that framework.
Action Comics No. 23 therefore ranks among the sought-after key issues of the series. A full overview of the most important comics is in our issues guide — and if you want to start at the very beginning, the Action Comics No. 1 reprint is the book that started it all.