Democrat Cory Booker says he will run for president in the 2020 election, joining a crowded field of candidates seeking the party's nomination.
The New Jersey senator, 49, was elected in 2013 after serving as mayor of the state's largest city, Newark.
He has been a vocal critic of President Donald Trump, slamming his administration's policies on issues such as immigration and climate change.
Mr Booker has long been touted as a rising star of the Democratic Party.
As Mr Booker aims to become the nation's second black president, his campaign launch falls on the first day of US Black History Month.
He has offered his first three interviews post-launch to radio programmes with black and Latino hosts, the New York Times reported.
Mr Booker's video announcement, entitled We Will Rise, focused on the emotions of America's civil rights movement, calling on the country to find a "common purpose".
Building on themes of community and sacrifice, he notes in his campaign video that he is the only senator who lives in a low-income, inner-city neighbourhood.
But Mr Booker will face tough competition in the party's primary, with a number of hotly-tipped candidates having already announced their intentions to run.
Kamala Harris, Elizabeth Warren, Kirsten Gillibrand, Tulsi Gabbard and Julian Castro will all contest the Democratic nomination.
It is the first time that more than one woman has competed for the party's candidacy.
Speaking on ABC's The View programme shortly after his reveal, Mr Booker described the upcoming battle with other Democrats for the nomination as just "sibling rivalry".
He emphasised that his campaign would focus on unity, saying: "This is a time when too many people are trying to pit people against each other."
Former New Jersey Governor Chris Christie, a Republican and former presidential candidate, told CNBC he liked Mr Booker personally, but it was "too early to figure out" if he was a frontrunner.
Who is Cory Booker?
The first black senator from New Jersey, Mr Booker grew up in Harrington Park, a mainly white, suburban town in the state.
Cory signs paperwork declaring his candidacy for president, his mom Carolyn by his side. pic.twitter.com/2KUXn4nUfN— Matt Klapper (@mattklapper) February 1, 2019
He played for his high school football team before going on to attend a number of top universities, including Stanford, Oxford and eventually Yale Law School.
After graduating, he moved to Newark to set up a non-profit organisation providing legal aid to poor families in difficult circumstances.
In the run up to his 2006 landslide election as mayor, he lived in a notorious housing project in the city and featured in a film that documented his campaign as a young, black, politician.
He was elected to Congress in 2013 by a significant margin, and became the second black member of the Senate at the time.
A silver-tongued senator
Analysis by Anthony Zurcher, BBC News
We've reached the point in the presidential pool party where candidates are no longer dipping their toes in the water, they're shouting "cannonball" and hurling themselves in.
On Friday Cory Booker rolled out an inspirational-style video and will be hitting the road in Iowa and South Carolina, starting what he hopes is the long journey to the Democratic nomination.
It will be hard to find a more gifted orator in the 2020 Democratic field than the New Jersey senator. He prowls the stage with a restless energy. His sentences are grandiose; he emotes every word.
If the presidential race were a declamation contest, Mr Booker would head the pack. And even though it's not, he still has a number of advantages.
His proximity to New York has made him a prodigious fund-raiser. His background reflects the diversity of the modern Democratic Party. His time as mayor of blue-collar Newark gives him a grounding to the plight of the underprivileged.
Many on the left don't trust him, however.
They view his big-money ties as a liability and haven't forgotten his 2012 defence of Republican Mitt Romney's venture-capital background.
In a crowded field, Mr Booker will be pressed to convince Democratic voters he's the one to take them to the promised land. His silver tongue will get quite a workout.
As a bachelor, Senator Booker has often faced questions about his sexuality from political opponents and journalists.
Last year, when asked about the speculation on the subject, he told the Philadelphia Inquirer that he is heterosexual.
"Every candidate should run on their authentic self, tell their truth, and more importantly, or most importantly, talk about their vision for the country," he said.
If elected, Mr Booker would become the first unmarried president since Grover Cleveland was elected in 1885.
He also regularly posts about his vegan diet and his exercise routine on social media.
View this post on Instagram
VEGAN BLISS As if the day could not get better, next to the Pride Festival in Asbury Park was the Vegan Festival. When Pride meets Vegan in an iconic Jersey town, all is good! The food was amazing and even more so, all the NJ vegan entrepreneurs were incredible people growing thriving business. Thank you to all the people I met, sorry I couldn’t put all the food and people in this post.
What does he stand for?
Mr Booker has called for reform of the criminal justice system, affordable healthcare and the legalisation of marijuana.
He is a progressive on social issues, supporting gun control, same-sex marriage, and he has previously tabled a bill that would outlaw "gay cure" therapy.
In a recent speech in Iowa, he spoke about gender equality and criticised President Trump's record on women's rights.
"We're not defined by a president who does not believe women," he said. "We're going to be defined when this state not only says that we believe women, but we elect women."
Mr Booker released classified documents relating to President Trump's Supreme Court nominee Brett Kavanaugh last year and vehemently opposed his nomination, stating that supporters were "complicit in evil".
His progressive views - and open criticism of the president on social media - has not gone unnoticed.
At a rally last October, Mr Trump said Mr Booker "did one of the worst jobs of any mayor" and "destroyed what he did, he was so bad".
The president has also targeted him on Twitter, posting in 2016: "If Cory Booker is the future of the Democratic Party, they have no future!"
Last year, the senator was among those targeted in a mail-bombing campaign that was aimed at critics of Mr Trump.
A suspicious item addressed to him was found at a mail facility in Florida.