Facebook has been fined €150,000 by France's data protection watchdog for failing to prevent its users' data being accessed by advertisers.
Watchdog CNIL said its fine was imposed on both Facebook Inc and Facebook Ireland.
The watchdog said the fine was part of a wider European investigation also being carried out in Belgium, the Netherlands, Spain and Germany into some of Facebook's practices.
The €150,000 fine is small in the context of the company, which has quarterly revenue of about $8 billion and a stock market capitalisation which stands at around $435 billion.
But it is the maximum amount the CNIL could fine when it started the investigation on the tech giant.
The CNIL can now issue fines of up to €3m, after the passing of a new law in October 2016.
Last year, the French watchdog had given Facebook a deadline to stop tracking non-users' web activity without their consent and ordered the social network to stop some transfers of personal data to the US.
Facebook argued that the Irish data protection authority, not the CNIL, was the competent authority to formulate such orders, as the social media company's European headquarters are located in Dublin.
In a statement today, Facebook did not say whether it would now take action as a result of the fine.
"We take note of the CNIL’s decision with which we respectfully disagree," Facebook said in a statement to Reuters.
"At Facebook, putting people in control of their privacy is at the heart of everything we do. Over recent years, we've simplified our policies further to help people understand how we use information to make Facebook better," it said.
The French order was the first significant action taken against a company transferring Europeans' data to the US after an EU court ruling last year that struck down an agreement that thousands of companies, including Facebook, had relied on to avoid cumbersome EU data transfer rules.
The transatlantic Safe Harbour pact was ruled illegal last year amid concerns over mass US government snooping.
EU data protection authorities said companies had three months to set up alternative legal arrangements for transferring data.
A new EU data protection law is set to enter into force in 2018, which could see companies get fined up to 4% of their global turnover if they fall foul of the new regulation.