US Supreme Court has ruled that same-sex marriage is a legal right across the United States.
It means the 14 states with bans on same-sex marriage will no longer be able to enforce them.
Justice Anthony Kennedy wrote that the plaintiffs asked, “For equal dignity in the eyes of the law. The Constitution grants them that right.”
It is unclear how soon marriage licences will be issued in states where gay unions were previously prohibited.
The ruling, which sparked celebrations outside the court in Washington DC, brings to an end more than a decade of bitter legal battles.
President Barack Obama said the ruling was a “victory for America”.
“When all Americans are treated as equal, we are all more free,” he said.
However, Christian conservatives decried the decision.
“We must resist and reject judicial tyranny, not retreat,” said Mike Huckabee, Republican presidential candidate and former Arkansas governor.
Loud cheers erupted outside the court after the ruling was announced, said the BBC’s Paul Blake at the Supreme Court.
Hundreds of people had camped out for hours awaiting the news.
One of the demonstrators, Jordan Monaghan, called his mother from his mobile phone amid the celebrations.
“Hey mom, I’m at the Supreme Court. Your son can have a husband now,” Mr. Monaghan said.
Minutes after the ruling, couples in one of the states that had a ban, Georgia, lined up in hope of being wed.
On social media, Democratic presidential candidate Hillary Clinton merely tweeted the word “proud” and the White House changed its Twitter avatar into the rainbow colours.
The case considered by the court concerned Jim Obergefell, an Ohio resident who was not recognised as the legal widower of his late husband, John Arthur.
“It’s my hope that gay marriage will soon be a thing of the past, and from this day forward it will simply be ‘marriage,’” an emotional Mr. Obergefell said outside the court.
The first state to allow same-sex marriage was Massachusetts, which granted the right in 2004.
In 2012, the high court struck down a federal anti same-sex marriage law.

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