The Democrat announced his bid with a video released by his campaign early Thursday morning.
In announcing his candidacy, de Blasio is seeking to claim a role on the national stage that has eluded him as mayor of the biggest U.S. city.
The 58-year-old could face obstacles in distinguishing himself in a field crowded with left-leaning Democrats.
He also faces skepticism at home. A recent poll found 76% of New Yorkers say they believe he shouldn’t run.
De Blasio has shrugged off bad polls, saying he believes his message of fighting financial inequality will resonate with everyday Americans.
On the campaign trail, he’ll be able to cite accomplishments such as expanding full-day prekindergarten citywide.