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The Duke of Sussex will share "mistakes and lessons learned" during his life in a memoir to be published next year.
Announcing the deal with publishers Penguin Random House, Prince Harry said he would share "the highs and lows" and be "accurate and wholly truthful".
Harry, who alongside his wife Meghan stepped back from royal duties last year, will donate proceeds to charity.
Penguin did not disclose the terms of its deal, which includes an audio book.
The duke, 36, said in a statement he would write the memoir "not as the prince I was born but as the man I have become".
He added: "I've worn many hats over the years, both literally and figuratively, and my hope is that in telling my story – the highs and lows, the mistakes, the lessons learned – I can help show that no matter where we come from, we have more in common than we think.
"I'm deeply grateful for the opportunity to share what I've learned over the course of my life so far and excited for people to read a firsthand account of my life that's accurate and wholly truthful."
Markus Dohle, of Penguin Random House, described the duke as being among "world-renowned leaders, icons, and change-makers we have been privileged to publish over the years".
A press release described the book as "intimate and heartfelt" and "honest and moving".
It added: "Prince Harry will offer an honest and captivating personal portrait, one that shows readers that behind everything they think they know lies an inspiring, courageous, and uplifting human story."
The BBC has contacted the Sussexes' representative for further comment.