LONDON — European Union regulators issued their first antitrust fine to Facebook parent Meta on Thursday with a penalty of $841 million for what they call “abusive practices” involving its Marketplace online classified ads business.

The European Commission, the 27-nation bloc’s executive branch and top antitrust enforcer, issued the penalty after its long-running investigation found that the company abused its dominant position and engaged in anti-competitive behavior.

It’s the first time the EU has imposed a fine on the social media giant for breaches of the bloc’s competition law.

Brussels has already slapped Big Tech rivals Google and Apple with billions in antitrust penalties.

The commission had accused Meta of distorting competition by tying its online classified ad business to its social network, automatically exposing Facebook users to Marketplace “whether they want it or not” and shutting out competitors.

It was also concerned that Meta was imposing unfair trading conditions with terms of service that authorized the company to use ad-related data — generated from competing classified ad platforms who advertise on Facebook or Instagram — to benefit Marketplace.

Meta’s practices gave it “advantages that other online classified ads service providers could not match,” Margrethe Vestager, the commission’s executive vice president in charge of competition policy, said in a news release “This is illegal under EU antitrust rules. Meta must now stop this behavior.”

Meta said in a statement that the decision fails to prove any “competitive harm” to rivals or consumers and “ignores the realities of the thriving European market for online classified listing services.”

The company said the Commission’s case ignores the fact that Facebook users can choose to “engage with Marketplace, and many don’t.” It said similar online marketplaces are continuing to grow. Meta said it would comply with the Commission’s order to end the offending conduct and not repeat it, but also vowed to appeal.