Denmark's artistic and chain-smoking Queen Margrethe II has been hailed for unifying and modernizing the monarchy in her 50 years on the throne, a milestone to be celebrated in pomp and circumstance this weekend.

The 82-year-old Margrethe, with her trademark white-haired bun, is the first woman to hold the position of reigning queen. And she has become the second longest-serving monarch in Danish history.

Having come to power amid waning support for the royals in 1972, she helped restore its standing in the decades that followed.

"She has managed to be a queen who has united the Danish nation in a time of large changes: globalization, the appearance of the multicultural state, economic crises in the 1970s, 1980s, and again in 2008 to 2015, and the pandemic," historian Lars Hovebakke Sorensen told AFP.

"The basis of her popularity is that the queen is absolutely non-political," he said.

Margrethe marked the 50th anniversary of her accession in January with a scaled-down celebration due to Covid. The full festivities were postponed until this weekend.

On Saturday, she will greet well-wishers from a palace balcony before lunch at the City Hall and an evening gala performance in her honor at Copenhagen's royal theatre.

Sunday's events will include a thanksgiving service at Copenhagen Cathedral, lunch on the royal yacht and a special dinner at the Christianborg Palace.

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Margrethe came to the throne at the age of 31 in January 1972 on the death of her father, Frederik IX.

At the time a mother of two young boys — she now has eight grandchildren — she was the first woman to become a reigning queen in one of Europe's oldest monarchies. The Danish royal line dates back to Gorm the Old in the 10th century.

Although she is the first reigning queen, she took her reign name Margrethe II, in recognition of Margrethe I, who ruled Denmark from 1375-1412 but never formally held the title.