It's a national (and sometimes international) affair that attracts throngs of well-wishers, close media attention, and high-profile guests all hoping to catch a glimpse of the happy couple.
Simple, white wedding dresses are traditional in some countries, perhaps with a bit of lace or beading to add to the design. Other royal brides celebrate with bright, festive colors, rich embroidery, and precious stones the size of eggs.
Here's what royal brides from around the world wore on their wedding day.
Princess Claire of Luxembourg wore a wedding gown by designer Elie Saab.
Princess Sofia of Sweden chose a lacy dress by Swedish designer Ida Sjöstedt.
Princess Charlene of Monaco's simple Armani gown was embellished with subtle embroidery.
Journalist Elisabetta Rosboch von Wolkenstein married the Prince of Belgium in Valentino.
Two billion people tuned in to watch Kate Middleton marry Prince William in a now-famous Alexander McQueen dress.
Bhutan's "Dragon Queen" Jetsun Pema was a commoner before marrying King Jigme Khesar Namgyel Wangchuck in a traditional Buddhist ceremony.
Princess Tatiana Blatnik of Greece wore a dress by Venezuelan designer Angel Sanchez.
The youngest daughter of Prince Richard of Sayn-Wittgenstein-Berleburg and Princess Benedikte of Denmark, Princess Nathalie's gown was created by Danish designer Henrik Hviid.
Viktoria Cservenyak, a former lawyer and writer, chose a dress by another Danish designer named Claes Iversen when she married Prince Jamie of the Netherlands.
Princess Noor of Jordan was radiant in a beaded wedding dress, though the couple divorced in 2009.
Morocco's Princess Lalla Salma, who worked as an engineer before taking the title, broke the tradition of keeping royal wives hidden when she married King Mohamed VI.
Indonesia's Prince Notonegoro and Princess Hayu were friends when they were younger, and dated for 10 years before marrying in a three-day-long wedding celebration.
Sayako Kuroda gave up her royal title as Princess of Japan to marry Yoshiyuki Kuroda in a plain, A-line dress and white gloves.