The event is all the more special for King Carl, as he becomes the first monarch in the country's history to celebrate a Golden Jubilee - plus, he is currently the second longest-reigning living monarch in Europe.
Friday sees a church service take place at the Royal Palace, followed by a televised speech from King Carl Gustaf, while Thursday's agenda included an opera performance at Drottningholm Palace outside Stockholm followed by a private dinner.
Read on for all the best-dressed European royals attending the special occasion.
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Princess Sofia
Princess Sofia of Sweden is a vision in yellow for her father-in-law's celebration, wearing head-to-toe lemon.
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Crown Princess Mary
Crown Princess Mary of Denmark's floaty floral gown made for the perfect choice for the royal occasion - and her husband, Crown Prince Frederik, looked equally smart on her arm.
Queen Margrethe II of Denmark and Queen Anne-Marie of Greece looked elegant in their jubilee outfits, arriving together for the special occasion. Margarethe opted for a pink paisley print pleated frock with a Barbie pink jacket layered over the top, while Anne-Marie wore a regal navy coatdress with a shawl draped over her arms.
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Queen Silvia
With her husband the man of the hour, it was no surprise that Queen Silvia of Sweden made a special effort with her outfit, wearing a powder blue suit with sensible heels.
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Princess Madeleine
Princess Madeleine of Sweden followed in her mother's stylish footsteps, also opting for a pale blue outfit for her father's big day.
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Crown Princess Victoria
Crown Princess Victoria didn't get the baby blue memo but looked sensational in her floral dress, accentuating the purple accents of her dress with her chunky headband.
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Princess Estelle
Crown Princess Victoria's daughter, Princess Estelle, looked super cute in her blue skirt suit, taking her aunt and grandmother's advice and wearing blue for the special day.
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Estelle was pictured grinning from ear to ear as her mother fixed her collar during their balcony appearance as the King oversaw the Changing of the Guard.
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Prince Oscar
Victoria's mum duties didn't end there, as she also made sure her son Prince Oscar looked picture-perfect. He was his father Prince Daniel's mini-me in a smart suit and blue tie, while Victoria ensured his hair was swept back away from his face.
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President Sauli Niinisto
Finland's President Sauli Niinisto and his wife Jenni Haukio arrive for the ceremony, with Jenni looking picture perfect in a white jacket and metallic skirt.
Stand by for more photos as they land, and in the meantime, brush up on your European royals below...
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