But it's also a significant occasion for his eldest son Prince William and 9-year-old grandson Prince George, who are now first and second in line to the throne. In fact, when William and Kate Middleton's son served as one of the Pages of Honor, he became the youngest future king to have an official coronation role.
"The fact that he is going to be such a big part of this coronation really demonstrates that his parents want him to have that understanding of the monarchy," royal correspondent Sharon Carpenter told E! News ahead of the big day, "and that appreciation and respect for the monarchy that starts at a very young age."
"Charlotte and Louis even being part of this coronation," she continued, "it's really introducing them to these very large events."
Indeed, Charles and Queen Camilla's coronation ushered in a new dawn for the kids.
"We're going to see a new era of the Wales kids being front and center," Sharon added. "It seems as if Kate and William are becoming more comfortable with that, because a big part of their mission as parents—just like Princess Diana—was to make sure their kids have as normal a childhood as possible."
And while Kate has taken on a new title since Charles became king, there is one role she's been fulfilling for more than a decade: No. 1 champion of her husband.
"This is going to be a really big day for her because she's there to support her father-in-law," Sharon noted. "She's there to support her husband, who's next in line for the throne, and this is a preview for him of what's to come."
To see more photos of George, Charlotte and Louis at the coronation, scroll on.