The book, due out at the end of next year, will share the “definitive tale” of its “experiences, adventures, losses and life lessons,” publisher Penguin Random House announced last night.
Prince Harry, who will donate the proceeds to charity, said he was “excited that people are reading a first-hand account of my life that is accurate and entirely truthful”.
The book marks the first time that a senior royal has ever written such a personal account in his life and the prospect is likely to send shockwaves through the royal family.
Buckingham Palace assistants declined to comment last night. It is not known whether the Queen or other senior family members were made aware of the project prior to its announcement.
The Duke has reportedly been working there for almost a year, as he and Meghan have confirmed they will not be returning as active members of the Royal Family.
He would have joined forces with the negro JR Moehringer, winner of the Pulitzer Prize, an American journalist and novelist.
The Duke said: “I am writing this not as the prince that I was born, but as the man that I have become.
“I have worn many hats over the years, literally and figuratively, and I hope that by telling my story – the ups and downs, the mistakes, the lessons learned – I can help show that little no matter where we come from, we have more in common than we think.
He added, “I am deeply grateful to have the opportunity to share what I have learned over the course of my life so far and delighted that people are reading a firsthand account of my life that is accurate and totally truthful. ”