Queen Beatrix of the Netherlands has abdicated her throne, handing over to her eldest son, Willem-Alexander.
He has become the first king of the Netherlands since 1890, ascending a throne largely stripped of political power but still invested with enormous symbolic significance for the Dutch people.
Around 25,000 well-wishers cheered outside the Royal Palace in Amsterdam as the abdication and automatic succession were broadcast live.
Crowds gathered in Dam Square from early this morning to see the new king and his wife, Queen Maxima, as they stepped onto the balcony of the Royal Palace.
Princess Beatrix blinked back tears as she presented her son.
She signed the abdication document in front of the Dutch cabinet, Willem-Alexander and Maxima.
"Today, I make way for a new generation," said Beatrix, 75, who took the title of Princess.
Willem-Alexander, a water management specialist, is expected to bring a less formal touch to the monarchy together with Maxima, a popular former investment banker from Argentina.
Queen's day - 30 April - is always a day for partying in the Netherlands.
Many people took yesterday off work and started celebrating in earnest with street bands and music.
Princess Beatrix chose to retire after 33 years in the role, following the tradition of her mother and grandmother.
Amsterdam has been awash with orange, the royal colour, for days.
Houses were covered in bunting and flags and shop windows were stuffed with orange cakes, sweets, clothes and flowers.
Nearly 1m people were expected to join the street party with dancing to bands and DJs, helping create a carnival atmosphere.
The royals are broadly popular, with 78% of Dutch in favour of the monarchy up from 74% a year ago, according to an Ipsos poll.
But they have been stripped of their political influence, and no longer appoint the mediator who conducts exploratory talks when forming government coalitions.