President Donald Trump has nominated Colorado federal appeals court judge Neil Gorsuch for the US Supreme Court.
If confirmed by the Senate, the 49-year-old would replace the vacancy left on the court by the late Justice Antonin Scalia.
The upper chamber’s Democratic leader has already said he has “very serious doubts” about the nominee.
The court has the last legal word on many of the most sensitive US issues, from abortion to gender to gun control.
Mr Trump said Judge Gorsuch had a “superb intellect, an unparalleled legal education, and a commitment to interpreting the Constitution according to text”.
“Judge Gorsuch has outstanding legal skills, a brilliant mind, tremendous discipline, and has earned bipartisan support,” Mr Trump added.
The announcement was made in the East Room of the White House in a primetime address on Tuesday evening.
Protests against Mr Trump’s choice were held outside the Supreme Court following the announcement.
In accepting the nomination, Judge Gorsuch said: “I am honoured and I am humbled.”
He was picked out of a shortlist of 21 possible choices that Mr Trump made public during the election campaign.
A conservative’s dream – Anthony Zurcher, BBC News North America Reporter
Donald Trump’s choice of Neil Gorsuch as his Supreme Court nominee is a fairly traditional pick in a decidedly untraditional time.
Judge Gorsuch has a CV and background that would make him a natural selection for just about any Republican president.
He’s the kind of Supreme Court nominee evangelical and traditional conservative voters dreamed of as a reward for sticking with Mr Trump through the general election despite campaign missteps, controversies and occasional political apostasies.
They knew they would get a court pick they wouldn’t like if Hillary Clinton won. They hoped they would get someone like Judge Gorsuch if Mr Trump prevailed.
Meanwhile, Democrats are left fuming over Senate Republicans’ precedent-breaking decision to stymie Barack Obama’s attempts to fill this court vacancy for nearly 10 months.
They have to decide if they will try to derail Mr Gorsuch’s nomination as retribution – perhaps forcing Republicans to break with another Senate tradition, the ability of a minority to a block a Supreme Court nominee with only 41 votes through a filibuster.
The party’s base, feeling a liberal majority on the court was stolen from them, will demand lockstep resistance, likely setting up a divisive confirmation fight ahead.
The Ivy-League educated jurist has the potential to restore the 5-4 conservative majority on the nine-seat high court.
The youngest Supreme Court pick in a quarter of a century, he is not expected to call into question high-profile rulings on abortion and gay marriage.
He is an “originalist”, meaning he believes the US Constitution should be followed as the Founding Fathers intended.
However, Senate Minority Leader Chuck Schumer suggested Judge Gorsuch may be outside the legal mainstream.
“Given his record, I have very serious doubts about Judge Gorsuch’s ability to meet this standard,” Senator Schumer added.
But Vice-President Mike Pence tweeted the nominee was “one of the most mainstream, respected, and exceptionally qualified Supreme Court nominees in American history”.