LONDON -- Choosing the "right" outfit to wear to any royal event is of utmost importance, and there can be few moments more historically significant than the coronation of a new monarch.
Much has been made of the departures from tradition for the coronation of King Charles III and this extended to the guest's dress codes. Gone were the requests for attendees to wear grand robes or ceremonial attire in favor of a more relaxed, pared-down look.
Scroll down to see what royalty, dignitaries and celebrities wore for the big event!
Kate, Princess of Wales
For the coronation of King Charles III and Queen Camilla Saturday, Catherine, the Princess of Wales and her daughter, Charlotte, donned special outfits for the once-in-a-generation occasion.
Princess Kate took what some royal watchers described as a toned-down approach by wearing a headpiece instead of a tiara.
The princess wore a floral headpiece with an ornamental silver braid, designed by Jess Collett x Alexander McQueen. The headpiece features leaf embroidery and crystal and silver thread work as well.
Kate also wore an ivory silk crepe dress and cape from Alexander McQueen that features floral motifs of daffodils, roses, shamrocks and thistles, symbolizing the four countries that make up the United Kingdom. She completed her look with diamond-and-pearl earrings that once belonged to Princess Diana, and the George VI festoon necklace, which was created in 1950 at the request of King George VI for his daughter, then-Princess Elizabeth.
Princess Charlotte, who just turned 8 Tuesday, wore a floral headpiece, also by Jess Collett x Alexander McQueen, which included a silver braid and crystal and silver thread work too.
Charles, Camilla wear ancient Robes of State
Charles and Camilla are each wearing a Robe of State as they enter Westminster Abbey.
Charles' robe was worn by his grandfather King George VI at his coronation in 1937.
Camilla's robe was originally made for Queen Elizabeth II's coronation in 1953. Underneath, her ivory, silver and gold embroidered coronation dress was by British designer Bruce Oldfield.
Jill and Finnegan Biden
First Lady Jill Biden wore periwinkle blue Ralph Lauren skirt suit accessorized with a coordinating hair bow and was accompanied by her granddaughter Finnegan Biden in a chic pale yellow cape dress by Markarian, in what could be seen as a sartorial nod to show solidarity with Ukraine.
Ukrainian First Lady Olena Zelenska
Ukrainian First Lady Olena Zelenska, who sat next to the Bidens, was spotted in an icy blue dress and coat pairing.
British actor and "Love Actually" star Emma Thompson arrived at the ceremony in a monochrome red rose-printed overcoat from Emilia Wickstead, accessorized with her Dame Commander of the Most Excellent Order of the British Empire (MBE) medal.
Thompson, who has been known to subvert royal dress codes after she received her MBE award at Buckingham Palace in 2018 in a pair of Stella McCartney for Stan Smith trainers, was seen outside Westminster Abbey this morning in a more opulent type of footwear: Roger Vivier black satin pumps with a crystal heel and buckle.
Katy Perry (scheduled to headline the coronation concert in Windsor on Sunday) opted for a pink skirt suit and pearl choker by Vivienne Westwood -- the late British designer who died in December 2022.
The distinctive necklace design may also be a nod to Queen Camilla's own fashion legacy. Camilla has numerous three-strand pearl pieces, including the aquamarine piece she has worn consistently since the 1990s.
Perry was accompanied by British Vogue editor-in-chief, Edward Enninful, who arrived in a statement icy blue waistcoat and polka dot tie.
Princess Anne, Charles' only sister, has joined royal family members at Westminster Abbey to watch her brother's coronation.
Anne and Charles were both alive when their mother was coronated in 1953. While Charles attended the ceremony, Anne did not because she was considered too young at the time.
Justin Trudeau and Sophie Grégoire Trudeau
Prime Minister of Canada, Justin Trudeau was spotted braving the rain on his way to Westminster Abbey. His wife Sophie Grégoire Trudeau cut through the gray weather with a blush-toned satin Ted Baker dress complete with organza sleeves.
Prince Akishino and Crown Princess Kiko of Japan
Across the event, international royalty used the moment to celebrate their country's traditional garments. Prince Akishino and Crown Princess Kiko of Japan appeared in a morning suit and muted patterned silk kimono with an obi belt respectively.
King Jigme Khesar Namgyel Wangchuck and Queen Jetsun Pema of Bhutan
The theme of traditional dress was continued by King Jigme Khesar Namgyel Wangchuck and Queen Jetsun Pema of Bhutan. King Jigme Khesar wore a Bhutanese Gho, while Queen Jetsun Pema wore a lilac-colored kira -- a customary wrap dress typical in Bhutan.
Queen Letizia of Spain
Often heralded as one of the world's best-dressed royals, Queen Letizia of Spain didn't disappoint, stepping out in a custom, amethyst-hued Carolina Herrera pink suit complete with ruffles and embroidered details.
Masenate Mahot Seeiso, Queen of Lesotho
Masenate Mahot Seeiso -- Queen of Lesotho, seen arriving with Lesotho's King Letsie III -- opted for an arresting, sapphire-blue paisley gown with a sculptural, off-the-shoulder bodice.
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ABC News contributed to this report.