Mother-in-law wears wedding dress to bride's big day, Twitter goes into meltdown

A bride’s mother-in-law wore a wedding dress to her son’s big day and Twitter cannot get over it.

There are many unwritten rules when it comes to wedding guest etiquette with perhaps the most important being, don’t wear a bridal gown unless you’re the actual bride.

It would be bad enough if a friend broke the fashion faux-pas, but imagine if your mother-in-law rocked up to your nuptials in a full-on frothy gown?

The unbelievable breach was brought to the Internet’s attention after Jimmy Fallon, asked people to tweet their best #weddingfail.

Thousands have joined in sharing some unbelievably cringe tales, from brides who were completely upstaged on their big day, to guests who laughed their way through the entire ceremony and best men who messed up their speeches.

But none were quite as shocking as the bride who confessed that the mother-of-the-groom donned an actual wedding dress for her son’s big day.

“My mother-in-law wore a wedding dress to my wedding. So, yeah, top that one, Twitter,” the user wrote alongside an image of two women both in floor-length white gowns.

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Unsurprisingly, people were pretty surprised by her tweet and within hours it had clocked up almost 28K likes, more than 5K retweets and countless comments from users who couldn’t get over the rule break.

READ MORE: Friends wear wedding dresses on night out following splits from cheating husbands

Since the tweet has gone viral, Amy, a romance author, later provided more of a back story, revealing that her mother-in-law grew up poor and is now therefore an extremely "frugal" woman.

She went on to say that the dress was "an incredible bargain" which her mother-in-law simply couldn't turn down.

And Amy certainly doesn’t hold a grudge about her mother-in-law’s outfit of choice for her big day.

"If you ask her now, she says she feels terrible about it,” she says.

"But she has more than made up for it since."

It isn’t the first time a mother-in-law horror story has lit up the Internet.

Earlier this year a new mum was left fuming after finding out her mother-in-law had convinced her husband to secretly change the spelling of their son’s name behind her back.

And back in March a woman shared her shock after her MIL asked for a refund of her wedding contribution because the bride doesn’t want children.