Siberry arrives on Broadway after originating the same role in the musical's national tour and performing it for two years.
In a statement, Spamalot director Mike Nichols said, "Michael Siberry has burned up the road as a brilliant King Arthur for a long time. So good was he in major cities all over the country that it became our hope that he could bring his funny, charming and, in the end, powerful Arthur to Broadway. That will now happen and we, the creators of the show, are very happy."
Siberry will join a company that features Tom Deckman, Rick Holmes, Bradley Dean, Robert Petkoff, Wally Dunn and Merle Dandridge. As previously announced, "American Idol" finalist Clay Aiken will return to the Spamalot cast Sept. 19.
Australian native Michael Siberry, an alumnus of England's Royal Shakespeare Company, made his Broadway debut in the RSC's revival of The Life and Adventures of Nicholas Nickleby. His Broadway credits also include The Merchant of Venice, The Sound of Music and The Frogs.
Siberry had been scheduled to be part of the cast of the fall revival of A Man for All Seasons, but his Spamalot casting will conflict. Michel Gill has been cast in Siberry's Seasons role of Duke of Norfolk. Spamalot features a book and lyrics by Eric Idle, music by John Du Prez and Eric Idle, direction by Mike Nichols, choreography by Casey Nicholaw and is based on the screenplay of "Monty Python and the Holy Grail" by Monty Python creators Graham Chapman, John Cleese, Terry Gilliam, Eric Idle, Terry Jones and Michael Palin.
The musical tells the tale of King Arthur and his Knights of the Round Table on their quest from God for the Holy Grail — with a short stop in the dazzling Spam-filled land of Camelot.
Spamalot earned the 2005 Tony Award for Best Musical and took home honors for direction (Mike Nichols) and one of its stars (Sara Ramirez).
Spamalot celebrated its third anniversary on Broadway March 18.
On Broadway Spamalot plays Tuesday-Friday at 8 PM, Saturday at 2 and 8 PM and Sunday at 2 and 7 PM.
For more information visit www.montypythonsspamalot.com.