Fiorina, the first female contender for the GOP nomination, has emerged as a vocal critic of Hillary Clinton in recent months, criticizing her State Department record and family foundation's acceptance of donations from foreign governments.
"She clearly is not trustworthy, about a whole set of things," Fiorina said this morning. "She peddled a fiction about [Benghazi, Libya] for a month, she hasn't been transparent about her server and her emails, and now we see now all of these foreign government donations to the Clinton Global Initiative."
In a video posted to her new campaign website this morning, Fiorina is shown watching Clinton's announcement video, before turning it off and saying that "America's founders never intended for us to have a professional political class."
Fiorina, who served as CEO of HP from 1999 to 2005, said her business management experience qualifies her to be president. "I understand executive decision-making, which is making a tough call in a tough time," she said.
She lost her 2010 Senate bid in California to incumbent Democratic Sen. Barbara Boxer by 10 points. In 2008, she served as an economic advisor to Sen. John McCain's presidential campaign.
In 2014, Fiorina founded the Unlocking Potential Project, an initiative to bring more female voters into the Republican Party.
Fiorina, 60, also sat down with ABC News’ Robin Roberts on "Good Morning America" today to discuss her new book, "Rising to the Challenge: My Leadership Journey." She will follow up her announcement with an online town hall event this afternoon, and will finish the week with a swing through Iowa, New Hampshire and South Carolina.