It's one of McDonald's best known burgers, but now a rival has won a case to prevent the fast food giant from trademarking the term "Big Mac."
The EU judgement, in favor of the Ireland-based Supermac's, revoked McDonalds registration of the trademark.
It said the world's largest fast food chain had not proven genuine use of it in the five years to 2017.
The ruling allows other companies to use the Big Mac name in the EU.
Supermac's, which sells a burger called the Mighty Mac, say they can now expand in the UK and Europe.
They say they've never had a product called Big Mac but that McDonalds had used the similarity of the names to block their growth.
McDonalds has a history of more successful litigation in trademark law.
In 1993, they blocked a dentist in New York from selling services under the name "McDental," and in 2016 they defeated an effort by a Singapore comapny to register the name "MACCOFFEE."