Claims have been filed on behalf of Prince Harry at the High Court, regarding alleged illegal interception of voicemail messages.
It's believed the Duke will allege he was the victim of unlawful information gathering for the purpose of publishing articles about him, possibly dating back to the early 2000s and when he had a mobile telephone as a teenager.
A spokeswoman for News Group Newspapers (NGN) - which owns The Sun and the controversial and now-defunct News of The World - said: "We confirm that a claim has been issued by the Duke of Sussex.
"We have no further comment to make at the current time."
A source at Reach plc, which owns the Mirror, said they were aware that proceedings had been issued, but had not yet received them so they were unable to comment further.
Files from the Courts and Tribunals Public Search and Office Copies confirm that the claimant is the Duke of Sussex and the defendants are News Group Newspapers Limited and MGN Limited.
The papers were filed on September 27.
This comes as the Duke's wife Meghan also filed her own lawsuit on Tuesday against the owner of the and its parent company Associated Newspapers, for allegedly unlawfully publishing a letter she had written to her estranged father Thomas Markle.
A Mail on Sunday spokesman said: “The Mail on Sunday stands by the story it published and will be defending this case vigorously.”
Could this lawsuit be detrimental to the reputation of theSussexes? Rachel Younger discusses.
It's reported the Duke of Sussex ignored the advice of some of his most senior aides over the timing of his statement, and not consulted his father the Prince of Wales, or brother William.
Harry said: “Though this action may not be the safe one, it is the right one.
“Because my deepest fear is history repeating itself. I’ve seen what happens when someone I love is commoditised to the point that they are no longer treated or seen as a real person.”
Harry said about his wife: “I have been a silent witness to her private suffering for too long. To stand back and do nothing would be contrary to everything we believe in.”