Gingrich's announcement, made on social networking websites Monday, came after months of public flirting with a bid. He enters a slow-to-form GOP presidential field that has left some Republicans craving more options as they search for a nominee strong enough to credibly challenge President Barack Obama.
The former Georgia congressman, well-known to most Republicans, brings to the race a years-in-the-making political machine with ties to early nominating states as well as a network of supporters and donors. But his personal baggage - he's acknowledged marital infidelity and has had two divorces - could hinder his chances of winning the party's presidential nomination more than a decade after leaving the House.
Still, he spoke confidently of wide support.
"I have been humbled by all the encouragement you have given me to run," Gingrich said in a Facebook posting that urged supporters to watch Fox News Channel on Wednesday. "I will be on to talk about my run for president of the United States."
Gingrich, 67, has spent months raising money, assembling a campaign team and visiting early primary-season states. He already has opened a headquarters in a suburb of Atlanta, and he will make his first speech as a candidate on Friday to the Georgia Republican Party Convention.