The Irish chain has more than 100 fast food restaurants in the country.
McDonald's has lost its exclusive claim to the "Mc" trademark on some of its food products within the EU, following a dispute with Irish fast food chain Supermac's.
The European Union Intellectual Property Office (EUIPO) ruled that the fast food giant had not proved genuine use of the "Mc" prefix on some of the products it trademarked.
This is Supermac's second partial victory this year in the EU branding dispute.
However, the EUIPO upheld McDonald's right to own the "Mc" trademark on chicken nuggets and some of its sandwich products.
The ruling also noted that each party must pay its own costs as both firms had succeeded in some parts of the case and failed on others.
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