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.
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.
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.
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.
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.
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.
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.
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...
Meet the Kings and Queens of Europe
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