Later, she changed into a colorful Valentino gown, accessorized with a pair of Valentino sneakers.

“Little known fact: I often wear sneakers under my evening gown,” Williams wrote in an Instagram post, with a shoutout to Valentino artistic director Pierpaolo Piccioli for giving them to her at the last minute. The tennis star added that she usually opts to stay comfortable on long nights.

Formality, of course, isn’t what it used to be, and sneakers have indeed grown into a cultural staple in their own right. Even luxury fashion labels recognize that they have to sell sneakers if they’re going to stay relevant—the comfy shoes are only getting more popular, at times at the expense of formal footwear such as heels. Sales of women’s sneakers jumped 37% in the US last year, while sales of high heels dropped 11%, according to data from research firm NPD Group.

Williams, who nabbed a call-out from Glamour as one of the best-dressed of the evening, in part because of her sneakers, has made her love of sporty shoes plain. At her own wedding, she wore a pair of bedazzled sneakers by Nike, her long-time sponsor.

So as long as the situation allows, go ahead and switch into some sneakers. Just make sure they’re clean and fresh, not a beat-up old pair, and opt for a casual lifestyle sneaker rather than something like a technical running shoe. It will pair better with non-athletic clothing.

Odds are the bride and groom will be thinking of your comfort anyway. At many weddings, women get flip-flops or slippers to change into. Even the royal couple handed out slippers for their reception.

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