The castings, announced Friday, come two weeks after Warner pushed production on the untitled Superman-Batman movie to the second quarter of this year and set a release date of May 6, 2016 as the studio departed from a July, 2015 slot.
Eisenberg is best known for portraying Facebook co-creator Mark Zuckerberg in “The Social Network,” for which he received an Oscar nomination.
Superman-Batman is in pre-production with Henry Cavill as Superman and Ben Affleck as Batman. “Man of Steel” director Zack Snyder is helming.
The Superman-Batman pic will also reunite “Man of Steel” stars Amy Adams, Laurence Fishburne and Diane Lane. Israeli actress Gal Gadot is coming on for the Wonder Woman/Diana Prince role.
“Man of Steel” grossed $668 million worldwide.
The screenplay is being written by “Argo” writer Chris Terrio from a screenplay by David S. Goyer. Charles Roven and Deborah Snyder are producing, with Benjamin Melniker, Michael E. Uslan and Wesley Coller serving as exec producers.
“Lex Luthor is often considered the most notorious of Superman’s rivals, his unsavory reputation preceding him since 1940,” Snyder said. “What’s great about Lex is that he exists beyond the confines of the stereotypical nefarious villain. He’s a complicated and sophisticated character whose intellect, wealth and prominence position him as one of the few mortals able to challenge the incredible might of Superman. Having Jesse in the role allows us to explore that interesting dynamic, and also take the character in some new and unexpected directions.”
Lex Luthor did not appear in last year’s Superman reboot “Man of Steel.” Gene Hackman played the role in the three “Superman” films opposite Christopher Reeve; Kevin Spacey took the part for 2006’s “Superman Returns.”
Irons is replacing Michael Caine, who portrayed Alfred in all three Christian Bale Batman films, directed by Christopher Nolan. Caine will turn 81 in March; Irons is 65.
“As everyone knows, Alfred is Bruce Wayne’s most trusted friend, ally and mentor, a noble guardian and father figure,” Snyder said. “He is an absolutely critical element in the intricate infrastructure that allows Bruce Wayne to transform himself into Batman. It is an honor to have such an amazingly seasoned and gifted actor as Jeremy taking on the important role of the man who mentors and guides the guarded and nearly impervious façade that encapsulates Bruce Wayne.”
Eisenberg next appears in “The Double” and “Night Moves.” Irons recently appeared in the television miniseries “The Hollow Crown” as Henry IV.