"We wanted to create something else for that audience," network chief Robert Greenblatt said of The Borgias.
Irons will play Rodrigo Borgia, the patriarch of the Renaissance-era Italian noble family known for its profound corruption. (Fun fact: Rodrigo was once the pope!) Yet to be cast are the roles of Rodrigo's sons, Cesare and Juan, and his daughter, Lucrezia, who, legend has it, was a talented poisoner.
Irons is best known for his Oscar-winning performance as Claus von Bülow in the 1991 biopic Reversal of Fortune.
Showtime has ordered 10 episodes of the series, which is executive-produced by film director Neil Jordan (The Crying Game) and Michael Hirst (The Tudors). The Borgias is scheduled to premiere in the spring of 2011.