Frederik X proclaimed the new King of Denmark after his mother Queen Margrethe II abdicates

Denmark's Prime Minister proclaims Frederik X as King after Queen Margrethe II abdicates, marking the first voluntary abdication in 900 years.

Denmark’s Prime Minister proclaimed Frederik X as King on Sunday after his mother Queen Margrethe II formally signed her abdication, with massive crowds turning out to rejoice in the throne passing from a beloved monarch to her popular son.

Ms. Margrethe, 83, is the first Danish monarch to voluntarily relinquish the throne in nearly 900 years. Many thousands of people gathered outside the palace where the royal succession was taking place, the mood jubilant as the Nordic nation experienced its first royal succession in more than a half-century, and one not caused by the death of a monarch.

Wearing a magenta outfit, Ms. Margrethe signed her abdication during a meeting with the Danish Cabinet at the Christiansborg Palace, a vast complex in Copenhagen that houses the Royal Reception Rooms and Royal Stables as well as the Danish Parliament, the prime minister’s office and the Supreme Court.

Prime Minister Mette Frederiksen next proclaimed Mr. Frederik King from the balcony of the palace before thousands of people — subjects of a kingdom where the trappings of royalty are mostly symbolic in today's modern era of constitutional democracy.

Mr. Frederiksen read the proclamation three times, which is the tradition, as Mr. Frederik stood beside her wearing a ceremonial military uniform adorned with medals. He was then joined on the balcony by new Queen Mary and the couple's four children, and the crowd spontaneously sang the national anthem.

“My hope is to become a unifying king of tomorrow," Mr. Frederik said. “It is a task I have approached all my life.”

“I want to return the trust I meet. I need trust from my beloved wife, you and that which is greater than us,” the new King said.