Watch: US woman dumps cheating boyfriend in 21st birthday speech

A US woman has posted an incredibly savage break-up video online, revealing she knew of her boyfriend's cheating during her own 21st speech.

Tiana Perea decided to dump her boyfriend in front of all their friends in her Texas home.

In the now-viral video posted by the birthday girl on Wednesday, Perea starts off the speech sweetly thanking her friends for coming to the party.

Then she turns to her now ex-boyfriend.

"I'd like to thank Santos for making me realise I deserve so much better," she says, to the shock of her boyfriend and their friends.

"Because every single person here knows you were trying to f**k with some girl... All of us have seen screenshots ... you were sexting her and sending her videos."

Warning: Video contains offensive language. 

Santos' face drops as Perea continues to reveal how much she knows.

"In case you didn't figure it out, we're over and you can get the f**k out," she says, pointing towards the door as her brother hands Santos a black bag presumably filled with his stuff.

Since she shared the brutal moment on Twitter, it's been viewed more than 5.8 million times.

In a later tweet, she invites followers to contact her "cause I'm single now".

It's not the first time a cheater has been called out so publicly. Last month, an Australian bride called an abrupt halt to her wedding by reading out her cheating fiancé's texts messages in front of their friends and family.