Princess Ingrid Alexandra of Norway celebrates her 21st birthday

Her Royal Highness is second in line to the throne

Crown Princess Mette-Marit (L), Crown Prince Haakon-Magnus (R) and Princess Ingrid Alexandra (C) greet the children's parade during the May 17 celebrations at their residence, Skaugum, west of the Norwegian capital Oslo, on May 17, 2024. Norway celebrate the signing of the country's constitution on May 17, 1814 with children's parades and school bands across the country. (Photo by Lise Ãserud / NTB / AFP) / Norway OUT (Photo by LISE ASERUD/NTB/AFP via Getty Images)

JANUARY 21, 2025 11:51 AM ESTJAN 21, 2025, 11:51 AM EST

Princess Ingrid Alexandra of Norway is celebrating a milestone birthday! Crown Prince Haakon and Crown Princess Mette-Marit's daughter turned 21 on Tuesday, Jan. 21.

The Norwegian Royal House commemorated the Princess' birthday with a carousel of photos of the future Queen, leading with a picture of her in fatigues at the Engineer Battalion in Brigade Nord, where "Private Alexandra" is stationed at Skjold Camp in Troms. The pictures also included a snapshot of her with her younger brother Prince Sverre Magnus that was taken during their aunt Princess Märtha Louise and Shaman Durek Verrett's wedding festivities last year.

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"Happy birthday, Princess Ingrid Alexandra! 🥳," the post was captioned (translated to English). "The princess, who is currently serving in the Armed Forces, turns 21 years old✨."

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Princess Ingrid Alexandra is currently second in line to the Norwegian throne, after her father, the Crown Prince. She is Haakon's first child with Mette-Marit. They also share 19-year-old son Prince Sverre Magnus. The Crown Princess has another son, 28-year-old Marius Borg Høiby, from a previous relationship. The Royal House's website notes that the Crown Prince and Crown Princess' daughter is "active and enjoys sports and outdoor activities," and "shares the joy of skiing and water sports with the rest of the Crown Prince Family."

Princess Ingrid Alexandra of Norway leaves Holmenkollen Chapel after the holiday service with in Oslo on Christmas Day, December 25, 2024. (Photo by Amanda Pedersen Giske / NTB / AFP) / Norway OUT (Photo by AMANDA PEDERSEN GISKE/NTB/AFP via Getty Images)

Princess Ingrid Alexandra, who graduated from high school in June of 2023, began her military training last year. In September, the Norwegian Royal House announced that Her Royal Highness' initial service had been extended from12 months to 15 months. At the time, the Royal House shared that the Princess, an engineer soldier, was starting her professional training and was serving as a gunner on a CV90 STING vehicle.

Norway's King Harald, Queen Sonja, Crown Prince Haakon, Crown Princess Mette-Marit, Princess Ingrid Alexandra, Prince Sverre Magnus pose for a group photo aboard the kingship Norway in the Geirangerfjord on August 31, 2024, where they attend Princess Martha Louise of Norway and her future husband Durek Verrett's wedding. Princess Martha Louise, the eldest child of King Harald will tie the knot on Saturday with American self-proclaimed shaman Durek Verrett. (Photo by Cornelius POPPE / various sources / AFP) / Norway OUT (Photo by CORNELIUS POPPE/NTB/POOL/AFP via Getty Images)

"I really enjoy my time here at Skjold. It's a varied everyday life, and there's a lot of exciting things we do. And I have to praise my company. They are incredibly good at motivating each other and doing well every day. Without them, I wouldn't have enjoyed it as much here," she told members of the press (translated to English) at Skjold Camp.

Princess Ingrid Alexandra of Norway greets the children's parade from the balcony of the Royal Palace in Oslo, on Norway's National Day on May 17, 2024. Norway celebrates the signing of the country's constitution on May 17, 1814 with children's parades and school bands across the country. (Photo by Heiko Junge / NTB / AFP) / Norway OUT (Photo by HEIKO JUNGE/NTB/AFP via Getty Images)

The Princess also admitted, "I have been challenged many times since I joined. I think the most important thing I have learned is that you can do much more than you think, and you are much stronger together. Whether it is in a team or in a squad or company, you can achieve much more when you are not alone."