Democrat Pete Buttigieg has thrown his hat into the ring for the 2020 US presidential election.
The mayor of South Bend, Indiana, said: "I belong to a generation that is stepping forward right now".
The 37-year-old is the ninth person to join the battle for the Democratic Party's nomination, in what is already a crowded race.
If he wins the nomination, Mr Buttigieg will be the first openly gay choice of a major political party.
He is also the youngest contender so far in the 2020 presidential race.
However, observers believe he may struggle to compete against other Democrats, who are more well known, and likely to raise more funds.
Senators Kamala Harris, Elizabeth Warren, Kirsten Gillibrand, representatives Tulsi Gabbard and John Delaney, and former secretary of Housing and Urban Development Julian Castro are among those who have also announced their intention to run.
Who is Pete Buttigieg?
He was first elected mayor of South Bend, which has a population of about 100,000, back in 2011 when he was just 29.
The video announcing he will run for president focuses on his role in the Rust Belt city's redevelopment and also takes aim at corruption and infighting in Washington.
"We can't look for greatness in the past, right now our country needs a fresh start," he says in the clip.
Mr Buttigieg is an Afghan war veteran and received a prestigious Rhodes scholarship in 2005 - following in the footsteps of other prominent figures like former President Bill Clinton.
He married Chasten Glezman, a middle school teacher, last year.
'A unique résumé'
Analysis by Anthony Zurcher, BBC News, Washington
Most stories published about Pete Buttigieg prominently mention that he is a millennial - a member of the generation born between 1981 and 1996. That isn't by accident.
The South Bend, Indiana, mayor isn't the only millennial in the 2020 race - Hawaii Congresswoman Tulsi Gabbard is also 37 - but Mr Buttigieg is positioning himself as a voice for the young. As he notes, his generation came of age in the aftermath of 9/11, were the ones who fought in subsequent US wars and struggled to establish a financial foothold amid the wreckage of the 2008 economic collapse.
Where their aging parents, the post-war Baby Boomers, may not be as concerned about the long-term impact of US policies, Mr Buttigieg says millennials will have to deal with the fallout from today's crises for decades.
Mr Buttigieg enters the race with a unique résumé. He's an openly gay veteran of the Afghanistan War and a Rhodes scholar. As mid-western mayor, he's shown he has voter appeal in a region that helped deliver the presidency to Donald Trump.
The march of time ensures millennials will run things someday. A Buttigieg presidency is a long shot for 2020, but his candidacy is a sign of things to come.
Mr Buttigieg ran for Democratic National Committee chairman in 2017, but dropped out when it was apparent he did not have sufficient support.
The 2020 Democratic presidential primary will be the first time more than one woman competes for the party's nomination.
The race is already thought to be record-breaking, with four women candidates running national campaigns.
He is due to release a book abut his life and career in South Bend in February.