The four girls won the public vote and beat hairdresser Marcus Collins, 23.
The girls brushed away tears as they told of their delight after the decision at the packed Wembley Arena in North London.
Leigh-Anne Pinnock, 19, said: "Oh my gosh, wow." Jade Thirlwall, 18, said: "I'm so grateful. Thank you for everybody who voted."
Perrie Edwards, 18, said: "Oh my gosh, that's insane."
And Jesy Nelson, 20, said: "Oh my God, this is never going to sink in. We can't thank the public enough for picking up the phone."
Sporting Marcus said: "The girls really deserve it. They are amazing. I'm really proud of myself. Thanks to everyone who voted."
He was first to sing, choosing an energetic version of Jackie Wilson's (Your Love Keeps Lifting Me) Higher and Higher as his song of the series.
Judge Louis Walsh told him: "You're a born little pop star." Marcus's mentor Gary Barlow added: "It was an amazing performance.
Little Mix followed with a note perfect version of En Vogue's Don't Let Go (Love). Louis said: "This time next year, this is going to be the biggest girl band in the UK."
Kelly Rowland added: "Y'all have performed your butts off!"
Tulisa Contostavlos, who mentored the girls, thumped her desk and screamed: "Vote for Little Mix!"
The four girls also sang a moving version of the carol Silent Night. [Source: The Sun]
