"Yes, I am running," Fiorina said on ABC's "Good Morning America." "I think I'm the best person for the job because I understand how the economy actually works. I understand the world; who's in it."
The ex-Silicon Valley executive and long-shot White House contender has never held public office. In 2010, she unsuccessfully ran for Senate in California, losing to Democratic Sen. Barbara Boxer.
She is now one of only a few women ever to seek the Republican Party's nomination for president -- among them, former Minnesota Rep. Michele Bachmann, who was a candidate in 2012, and former North Carolina Sen. Elizabeth Dole, who made a brief run in the 2000 cycle.
Fiorina has been laying the groundwork for a possible presidential campaign over the past few months, traveling to early states like Iowa and New Hampshire and meeting with activists and donors.
Casting herself as an outside-the-beltway candidate with years of private sector experience, she has been particularly critical of former Secretary of State Hillary Clinton and her work in government.
On Monday, Fiorina said Clinton "clearly is not trustworthy."
"She has not been transparent about a whole set of things that matter," Fiorina said on ABC, ticking off Benghazi, Clinton's use of personal emails at the State Department as well as foreign donations that the Clinton Foundation has received.
And a video posted on her newly unveiled campaign website, carlyforpresident.com, kicks off with a shot of Fiorina watching Clinton's campaign announcement video."If you're tired of the sound bites, the vitriol, the pettiness, the egos, the corruption; if you believe that it's time to declare the end of identity politics; if you believe that it's time to declare the end of lowered expectations; if you believ that it's time for citizens to stand up to the political class and say enough, then join us," Fiorina says.
Fiorina also announced the news of her campaign on various social media outlets including Twitter. She is set to participate in an online town hall with supporters Monday afternoon, then travel to Iowa, New Hampshire and South Carolina later in the week. Her new book, "Rising to the Challenge," is scheduled to be released on Tuesday.
Standing out in what is expected to be a crowded Republican field that includes far better-known candidates like former Florida Gov. Jeb Bush, Florida Sen. Marco Rubio and Wisconsin Gov. Scott Walker, will be a significant challenge for Fiorina.
But political strategists say Fiorina, an articulate communicator and energetic retail politician, could very well have a moment in the race, particularly as she makes an appeal to voters who are drawn to a non-establishment candidate.
Fiorina could also be a galvanizing force in an election where on the other side of the political aisle, Clinton -- the widely presumed Democratic frontrunner -- has indicated that she plans to make gender issues one of the central themes of her campaign.
Marty Wilson, an executive vice president at the California Chamber of Commerce who managed Fiorina's 2010 Senate campaign, said one potential obstacle for Fiorina will be building up a national donor base when she hasn't had to raise money for a political campaign since 2010.
"She's a very talented candidate and connects well with voters," Wilson said. "The problem is after 2010, she was no longer a candidate. So mail lists and email lists tend to atrophy when they're not in use."