THE Netherlands' Willem-Alexander becomes Europe's youngest monarch when Queen Beatrix abdicates and his country hails the avowedly 21st-century king with a massive orange-hued party.
Willem-Alexander, 46, will be the first Dutch king in 122 years (since 1890) and the first of a new wave of European monarchs, whose ageing blue blood - average age 71 - is increasingly watered down.
Amsterdam's population is set to double with at least 800,000 visitors flooding the city's streets and canals as Beatrix, 75, ends her 33-year reign on Tuesday by signing the act of abdication at the royal palace.
While Beatrix was known for her formal court, Willem-Alexander has already said that he and his glamorous Argentine-born queen consort Maxima, 41, will not be "protocol fetishists".
Parliament last year stripped his mother of her last remaining role in forming governments, and the new king has said he would accept a purely ceremonial role should parliament so decide.
The Dutch monarch's current political role is restricted to signing laws and meeting regularly with the prime minister.
The king will be sworn in rather than crowned at the deconsecrated Nieuwe Kerk, a stone's throw from the palace, before a joint session of the houses of parliament.
Sixteen MPs have refused to take an oath in front of the king, saying that they have already pledged allegiance to the constitution and cannot now do so to a person.
Four Socialist MPs are staying away, and the other 12 have been told to sit at the back of the church.
Beatrix's enthronement in 1980 was marred by violent protests and running street battles over a housing crisis that left the city looking like a war zone.
Anti-royalists this time have been allotted six locations in Amsterdam to stage protests. But only one had been booked by Republicans planning playful protests, including by wearing white.
Republicans have started a petition to reduce the king's 825,000-euro ($A1.06 million) salary to get the matter debated in parliament.
Willem-Alexander noted ahead of his enthronement that if his budget were cut then he would have to reduce his staff, adding to the ranks of the country's ever growing unemployment rate, currently 8.1 per cent.
Preparations for the day have been overshadowed by a rancorous debate about the event's official song, known as the Koningslied.
An online petition rejecting the song, an unusual mix of traditional and rap music, garnered 40,000 signatures within a few days.
Composer John Ewbank withdrew the song but the enthronement organising committee stuck with it.
The nation will now sing the Koningslied as one on Tuesday evening, just before the royal family heads off on a water pageant behind Amsterdam's central train station.
A cornucopia of concerts and club nights has been organised around the city, including an open-air set by world-famous Dutch DJ Armin van Buuren, and orange-themed street parties are planned across the nation.
The day will also be tinged with sadness for Maxima, whose father, Jorge Zorreguieta, and mother will be notable by their absence.
Zorreguieta, 85, a minister under the notorious Argentine regime of general Jorge Videla in the 1970s, also had to miss his daughter's 2002 marriage because of doubts over his role in the murderous junta.
Maxima is largely responsible for having made her husband popular after an allegedly boozy youth which earned him the nickname "Prince Pils".
The ever-smiling Maxima has mastered the Dutch language and even took a charity swim in Amsterdam's canals, endearing herself further in a country that expects their royals to be at once normal and regal.
Willem-Alexander's brother Friso will also be missed, in a coma following a skiing accident in Austria in February 2012.
The day's ceremonies will be attended by those waiting in line for thrones around the world, reportedly including Britain's Prince Charles, Spain's Prince Felipe and Japan's Prince Naruhito.
Willem-Alexander and Maxima's three daughters, including future queen Catharina-Amalia, 9, will be at their parents' side during the day.
