"After prayerful consideration with my family and closest friends, I have decided to seek the Republican nomination for president of the United States," Cain said. "I look forward to continuing my travels across the country, engaging in discussions with the American people about the concerns facing our nation and sharing my 'common sense solutions' with them."
"In case you accidentally listen to a skeptic or doubting Thomas out there, just to be clear ... I'm running for president of the United States, and I'm not running for second," he said.
"Let me tell you what the Cain Doctrine would be: We ain't raising the debt ceiling," he said, to loud cheers. "We are going to cut cut the spending."
The 65-year-old businessman has worked as for Coca-Cola, Pillsbury, Burger King, Godfather's Pizza and the National Restaurant Association before hosting his radio program, "The Herman Cain Show," broadcast out of Atlanta.
He hit the political stage in 1994, when he argued with President Clinton over the Democrat's health care plan at a televised town hall meeting. In 2004, Cain lost a three-way Republican U.S. Senate primary bid in Georgia with one-quarter of the vote.
Cain has said he supports a strong military, lower taxes, less regulation, a return to the gold standard and he has openly been critical of President Obama's health care plan.
In 2006, Cain was diagnosed with liver and colon cancer. He says he's been cancer-free since 2007, and credits the American health system for his recovery.
On the day of his announcement, Cain wrote a case for his presidency on Foxnews.com called "Solving for X."
"Throughout my own [life], 'solving for x' meant learning how to nurture a family, how to navigate the corporate world during unfavorable times and how to deliver results," he writes. "In delivering these results, I have always maintained a sense of humanity while achieving bottom lines and profitability. It stems from my humble beginnings, upbringing and spiritual compass.
"In the end, it will be up to the American people. They will decide if my 'common sense solutions' make up the proper formula to 'solve for x.'"
Cain joins former a still unsettled GOP field that includes Newt Gingrich, the former speak of the House, who formally announced his candidacy last week, and former Minnesota Gov. Tim Pawlenty, who is expected to formally announce on Monday.