US President Donald Trump has nominated Brett Kavanaugh for the Supreme Court, setting the stage for a bruising confirmation battle.
In a primetime announcement at the White House, Mr Trump praised his pick as a "brilliant jurist".
The nominee, a District of Columbia appeals court judge, is a former adviser to ex-President George W Bush.
The decision has far-reaching implications for America on everything from abortion to guns to immigration.
This is Mr Trump's second appointment to the highest court in the land, potentially allowing him to shape the US for a generation after he leaves office.
The president said: "Judge Kavanaugh has impeccable credentials, unsurpassed qualifications and a proven commitment to equal justice under the law."
Mr Trump added: "He is a brilliant jurist with a clear and effective writing style, universally regarded as one of the finest and sharpest legal minds of our time."
Image captionJudge Kavanaugh said he was "humbled" by the president's confidence in him
With reality television-style suspense, the president had kept everyone guessing up until the last moment.
The appointee would replace Justice Anthony Kennedy, 81, who announced last month that he will retire this summer.
At Monday night's announcement in the East Room, Judge Kavanaugh, 53, said: "Mr President, thank you. Throughout this process I have witnessed firsthand your appreciation for the vital role of the American judiciary.
"No president has ever consulted more widely, or talked with more people from more backgrounds to seek input abut a Supreme Court nomination.
"I am grateful to you and I am humbled by your confidence in me."
Image captionPro-choice and anti-abortion protesters demonstrate in front of the US Supreme Court ahead of the announcement
Who is Judge Kavanaugh?
He has served since 2006 on the influential US Court of Appeals for the District of Columbia Circuit and was formerly a White House aide under George W Bush.
He previously worked for Kenneth Starr, the independent counsel who investigated Democratic former President Bill Clinton in the 1990s.
A Yale graduate and devout Catholic who went to a Jesuit high school, he once clerked for Justice Kennedy, the man he would replace.
Judge Kavanaugh recently voiced disagreement with a court decision allowing an undocumented teenage immigrant to have an abortion.
He wrote a Minnesota law review article in 2009 arguing that presidents should be shielded from criminal investigations and civil lawsuits while in office.
Analysts say that could have weighed in his favour with the White House, given that the Supreme Court may at some point be asked to rule on matters arising from Special Counsel Robert Mueller's ongoing Russia-related investigation.
What's at stake?
The US Supreme Court is the ultimate arbiter on contentious laws and disputes between states and the federal government.
It rules on such issues as abortion, the death penalty, voter rights, immigration policy, campaign finance and racial bias in policing.
Media captionExplaining Roe v Wade and abortion in US
Each of the nine justices holds a lifetime appointment. Judge Kavanaugh is relatively young, meaning he could serve for decades to come.
His appointment will not change the ideological tilt of a court that already has a 5-4 conservative majority, but he could nevertheless shift the bench further right.
Justice Kennedy sometimes sided with the court's liberal justices on divisive social issues. But Judge Kavanaugh may not be so accommodating.
Neil Gorsuch, 50, who was appointed by Mr Trump last year, is already one of the court's most conservative justices.
Image captionJudge Kavanaugh was accompanied by his wife and two daughters
A safe pair of hands
Analysis by Anthony Zurcher, BBC News, Washington
The front-runner was a front-runner for a reason.
Over the weekend, it looked like Judge Kavanaugh's star may have been fading, that perhaps he had too-close ties to the Bush family for Mr Trump's liking. In the end, however, the safe pick won out.
He is the kind of judge a President Jeb Bush or Mitt Romney would have picked - a man with an established legal pedigree and a reputation as a reliably conservative jurist.
If the party sticks together, the president's choice will be sitting on the Supreme Court when its new term starts in October.
President Trump campaigned with a promise to conservatives that he would fill the federal courts, from the top on down, with judges to their liking.
It's a promise that has helped cement near-record levels of support for his presidency from Republican voters - and for good reason.
Mr Trump is securing a conservative judiciary for a generation.
The nominee must be confirmed by the US Senate, which the Republican president's party narrowly controls 51-49.
A nominee needs a simple majority of 51 votes to be confirmed.
With Senator John McCain battling cancer in his home state of Arizona, Republicans can currently only muster 50 votes.
Before a full vote on the chamber floor, the prospective justice will be grilled by the Senate Judiciary Committee in hearings that can go on for days.
Judge Kavanaugh said he would begin meetings with senators on Tuesday.
Democrats are certain to press Mr Trump's latest nominee on the landmark 1973 Roe v Wade ruling that legalised abortion nationwide.
Conservative Christians have long vied to overturn that decision, and Mr Trump has previously said he wants "pro-life" justices opposed to abortion rights.
The White House and Republican party want the nomination in the bag before November's mid-term elections.
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Image captionFirst Lady Melania Trump looks on before President Trump introduces Judge Kavanaugh
All eyes on which senators?
Conservative judicial activists will immediately begin running ads pressuring politically vulnerable Democratic senators to vote for confirmation.
Joe Donnelly of Indiana, Heidi Heitkamp of North Dakota and Joe Manchin of West Virginia will be prime targets.
All three face gruelling re-election campaigns this year in their conservative states. All three joined with Republicans in confirming Justice Gorsuch.
Meanwhile, liberal groups are already calling on two moderate Republican senators - Susan Collins of Maine and Lisa Murkowski of Alaska - to reject the nominee.
Ms Collins has said she will not vote for any candidate who threatens abortion rights.
Activists have sent coat hangers - an abortion rights symbol - to her office.