Celebrations are underway for the royal baby's birth and congratulations for the Duke and Duchess of Sussex are still coming in from around the world.

From lighting up Niagara Falls blue, to planting trees and potentially posting a pavlova, here's some of the ways the rest of the world reacted to Prince Harry and Meghan's good news about Baby Sussex.

  • 'Royal births' in San Francisco

A hospital in San Francisco must have been planning the long-awaited day for a while, providing knitted crowns for the heads of babies born on Monday.

Trevor and Brittney Moore gave birth to little Harlow at Sutter Health's California Pacific Medical Center, and she was among the first to sport the crown that the family will “keep forever”.

New dad Trevor said: “Well, our news today is we got to welcome little Harlow Moore to the world. And we're fortunate enough to spend it with the royal family as well.

“We saw on the news this morning that they invited their boy into the world, so kind of cool that we get to share the same day with our daughter as well.”

  • Niagara Falls turns blue

Over in Canada, CBC Toronto reported the famous Niagara Falls shone a royal blue to mark the boy's birth.

The lights went on between 8.30pm and 9.30pm local time.

  • Congratulations from New Zealand

From the other side of the world, congratulations also came from New Zealand’s Prime Minister Jacinda Ardern – and she had a gift ready too.

Ms Ardern said New Zealand would make a donation to a group called Little Sprouts, which prepares baby boxes for families in need.

She also said the government would buy 10 native trees to be planted in New Zealand to acknowledge the birth.

  • Australian Prime Minister says 'it doesn't get better than that'

Just across the water from New Zealand, Australia’s Prime Minister Scott Morrison said the arrival of baby “doesn’t come any better than that”.

He reminisced about the time the Duke and Duchess of Sussex visited Australia and Harry “smashed” his wife’s Pavlova dessert, and suggested sending the family another to mark the birth.

  • Celebrities give their thoughts in New York

Joan Collins and Naomi Campbell had their say too. Credit: PA

Meanwhile, at the Met Gala in New York, Joan Collins chipped in with her own sort of congratulations – telling a reporter “it’s about time”.

Naomi Campbell was a bit more direct with her well-wishes, saying “it’s fantastic, congratulations”.

  • Amy Schumer's baby boy

Comedian Amy Schumer and her husband also welcomed their baby boy to the world.

She broke the news on Instagram, saying simply: “10:55pm last night. Our royal baby was born.”