"I have decided to be a candidate in the 2017 presidential election," Sarkozy, who was president between 2007 and 2012, wrote in a foreword to a new book to be released Wednesday and seen by AFP.
"I felt I had the strength to lead this battle at a troubled time in our history," he added.
Sarkozy, 61, also posted a link to the extract on his Twitter account.
"The next five years will be filled with danger but also with hope," wrote the 61-year-old conservative, who had made no secret of his ambition to return to the top job.
He listed five major challenges for France, which included defending French identity, restoring lost competitiveness and enforcing state authority.
The announcement of his bid to secure the nomination of his opposition Republicans at a party primary in November comes in the midst of an impassioned debate over the place of Islam in French society.
Sarkozy said France's "top battle" was over how "to defend our lifestyle without being tempted to cut ourselves off from the rest of the world."
It comes as no great surprise that Sarkozy has announced his presidential ambitions, with another book he penned in January this year widely seen as the launchpad for his presidency bid.
In the book he revisited a few infamous moments during his time as president and admitted the error of some of his choices, including when he was filmed telling a farmer to "piss off your poor idiot" at an agricultural fair.
"I myself was very wrong during a visit to the agricultural fair, to give in to provocation by responding to the individual who insulted me. It was a mistake, for he had the right to say what he wanted, albeit he didn't have to say it like that," he wrote.
"I learned the hard way that having a strong character does not allow you to do anything."