Slinger, who recently appeared in Urinetown, will join the cast of Charlie and the Chocolate Factory on 4 May 2015.
His extensive appearances with the RSC include the title roles in recent productions of Hamlet, Macbeth, Richard II and Richard III.
Charlie and the Chocolate Factory is directed by Sam Mendes.
It features music by Marc Shaiman, lyrics by Scott Wittman and Shaiman, a book by David Greig, set and costume designs by Mark Thompson and choreography by Peter Darling.
It's produced at the Theatre Royal, Drury Lane by Warner Bros. Theatre Ventures, Neal Street Productions and Langley Park Productions.