There are a few fairly self-explanatory rules at a wedding - stand when the bride comes down the aisle, keep speeches family-friendly... and the main one - don't outshine the bride.
But one wedding guest seems to have forgotten that last one, after donning a floor-length, silky, white number to a friend's wedding.
The anonymous scene-stealer posted a glowing review of the dress on online store Shien, writing the show-stopping number was the "perfect size".
"I like it so much and I wore this to a wedding and everybody kept looking at me," she gushed in the review.
"So sexy and simple."
The review was promptly screenshotted and shared to popular sub-Reddit 'Wedding Shaming' this week, with a fairly unflattering pig's head emoji placed over the woman's face.
"Of course they were looking at you love, you’re literally wearing a wedding dress to someone’s wedding!" the Reddit user captioned the post.
Other Reddit users voiced their own shock, with one commenter writing that it was "tacky af".
"That's a good way to piss a few people off," wrote another.
It's not the first wedding fashion faux pas to make headlines. Earlier this year a woman arrived at her son's ceremony ins a strapless, fishtail white gown.