Lawyers representing the Saul Zaentz Company (SZC), the American firm which owns the copyright to a number of J.R.R. Tolkien's works, have ordered the pub in Southampton, England to change its name or face legal action.
British actor Stephen Fry has already pledged his support to the campaign, and now McKellen, who stars in the eagerly-awaited The Hobbit movie, has followed suit.
Referencing the world created in Tolkien's book, he posted on Twitter.com, "Lawyers of Mordor retreat."
The pub has been trading as The Hobbit for more than 20 years and landlady Stella Mary Roberts insists she doesn't have the funds to fight the legal threat.