Donnelly, who is currently appearing as the lead Deco in The Commitments at the Palace Theatre, joins the previously announced Beverley Knight.
Donnelly's previous West End credits include Les Miserables, The Phantom of the Opera and Billy Elliot. He appeared in the 25th Anniversary concert of Les Miserables at the O2 Arena as Courtfeyrac, and also appeared in the film version as Combeferre.
Memphis, the 2010 Tony winner for Best Musical that also won Tonys for its book (by Joe DiPietro) and score (with music by David Bryan, and lyrics by Bryan and DiPietro), is produced in London by Junkyard Dog Productions, Marlene and Kenny Alhadeff, Barbara Freitag, Joseph Smith and John Brant.
To book tickets, contact the box office on 020 7379 5399, or visit memphisthemusical.com.