Prince Harry is suing the Mail on Sunday as he and wife Meghan Markle continue their war against the British media.
The 36-year-old filed the new lawsuit in late November against Associated Newspapers, reportedly over an article it ran in October which claimed he had lost contact with the Royal Marines.
The Duke of Sussex has employed high-profile law firm Schillings, who represented US actor Johnny Depp in his failed lawsuit against The Sun this year.
Details within court documents are unclear though it's expected more information about the case in London's High Court will come to light in coming weeks.
The lawsuit marks the sixth defamation case launched on behalf of the couple, who are ramping up their relentless pursuit against UK tabloids.
Meghan is also suing the Mail on Sunday over a 2018 article which published excerpts of a letter she sent to her father, Thomas Markle, claiming it breached her privacy. The case is ongoing.
"Unfortunately, my wife has become one of the latest victims of British tabloid press that wages campaigns against individuals with no thought to the consequences – a ruthless campaign that has escalated over the past year, throughout her pregnancy and while raising our newborn son," Harry wrote in a statement on the royal family's official website in October last year.
Days later, Harry also began legal proceedings against publishers of The Sun and The Daily Mirrornewspapers, alleging illegal phone interception years ago.
Harry was forced to step down from his role as Captain General of Royal Marines when he quit royal life in March and moved to the US with Meghan and their one-year-old son, Archie.
Harry served in the army for over 10 years. He launched the Invictus Games in 2014, which supports injured or sick armed services personnel and allows them to compete in sports.
As per the sussexroyal.com website, a section titled Spring 2020 Transition states Harry's intention to stay in touch with the military and maintain his rank over the course of the 12-month review into their post-royal life.
"In relation to the military, the Duke of Sussex will retain the rank of Major, and honorary ranks of Lieutenant Commander, and Squadron Leader. During this 12-month period of review, the Duke's official military appointments will not be used as they are in the gift of the Sovereign.
"No new appointments will be made to fill these roles before the 12-month review of the new arrangements is completed," the website says.
"While per the agreement, the Duke will not perform any official duties associated with these roles, given his dedication to the military community and ten years of service he will of course continue his unwavering support to the military community in a non-official capacity."