Law firm Austen Hayes, which said the lawsuit is being filed at the High Court, said thousands of Grindr users in the United Kingdom may have been affected.
The firm claims users' highly sensitive information, including HIV status and the date of their latest HIV test, were provided to third parties for commercial purposes.
Grindr said in a statement provided to The Guardian newspaper that it planned to “respond vigorously to this claim, which appears to be based on a mischaracterisation of practices from more than four years ago".
Austen Hayes said around 670 people had signed up to the lawsuit over breaches said to have taken place between 2018 and 2020, with potentially thousands more joining the case.
Austen Hays' Managing Director Chaya Hanoomanjee said in a statement: “Grindr owes it to the LGBTQ+ community it serves to compensate those whose data has been compromised and have suffered distress as a result, and to ensure all its users are safe while using the app, wherever they are, without fear that their data might be shared with third parties."
Grindr stopped sharing users’ HIV status with third-party companies in April 2018 after Norwegian researchers revealed data sharing with two companies.
Three years later, the country’s data protection authority fined Grindr 65m Norwegian krone (£4.8m), a decision the company appealed.
However, that decision did not centre around alleged sharing of users’ HIV status, but instead focussed on the sharing of the fact that users were signed up to Grindr - which it found was sensitive information.
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A Grindr spokesperson said: “We are committed to protecting our users' data and complying with all applicable data privacy regulations, including in the UK.
“Grindr has never shared user-reported health information for “commercial purposes” and has never monetised such information.
“We intend to respond vigorously to this claim, which appears to be based on a mischaracterisation of practices from more than four years ago, prior to early 2020.”