Facebook is being sued in Austria over alleged privacy violations and claimed participation in the US National Security Agency’s (NSA) PRISM programme.
An Austrian law graduate called Max Schrems is leading the class action lawsuit on behalf of around 25,000 Facebook users based in Europe and beyond.
Among them are more than 1,000 people from the UK and Ireland.
Germany, regarded as one of Europe’s more privacy-conscious countries, has the highest number of people backing the case with more than 5,000 users.
The hearing is set to begin in Vienna, where Mr Schrems will say Facebook took a “Wild West” approach to data protection.
“There is a wide number of issues in the lawsuit and we hope to kind of win all of them and to get a landmark case against US data-gathering companies.”
The case has been brought against the social network’s European headquarters in Dublin.
All accounts outside the US and Canada are registered there – around 80% of the site’s 1.3 billion users.
Mr Schrems is seeking compensation of around £360 per user.
In June 2013 Facebook founder Mark Zuckerberg denied that Facebook had taken part in the NSA’s spying programme to share user information with the US government.