The 36-year-old prison officer triumphed over teenager Nicholas McDonald in Sunday night's (15 December) live finale, becoming the first ever Overs category act to win. She had over one million votes.
Her prize is a recording contract and the chance to support Beyoncé on tour. She'll release the Demi Lovato ballad 'Skyscraper' as her winner's song.
Sam, who was mentored by Sharon Osbourne, had been the bookies' favourite to scoop the crown for weeks but still looked stunned when Dermot O'Leary revealed the results of the public vote.
Sam said: "I just want to say I love Nicky McDonald to pieces. He needs an album out as well. He has an amazing voice."
Nicholas said: "If I was to be beaten by anybody it was to be Sam. She was a hard one to beat. Thank you to everyone who has voted for me. I'll have an album out. Love you all."
Sam was praised by the judges – including Gary Barlow, Nicole Scherzinger and Louis Walsh – every week thanks to her powerful vocal performances and the finale was no different as she wowed with a duo of strong performances on Saturday night.
She kicked off her finale weekend with a performance of Lady Gaga's 'The Edge of Glory' which had Gary predicting her as the winner. "She was unbelievable," he said. "She smashed it." Next up was a duet of 'And I'm Telling You' alongside a stunning looking Nicole.
On Sunday night, she had to perform her best song of the series and she chose 'The Power Of Love' by Jennifer Rush, before reducing Nicole and Sharon to tears with her rendition of Demi Lovato's 'Skyscraper', which she has chosen as her winner's song.
"It's almost like you've done this on behalf of people whose dreams have stayed dreams," said Gary. "You've had a massive second chance and it's been a pleasure watching that and being part of your journey."
Nicole wiped away tears as she said: "You got me looking like a hot mess up here… That voice is a gift from God and you are the voice for so many out there. Timing is everything and everything in his time. This is your time right here."
Louis said she deserved to be on the stage and deserved a recording contract. "That is going to be a number one record," he predicted.
Sharon, who was in tears, struggled to speak.
Sunday night's finale began with all the former contestants (had you forgotten any of them?) returning to the stage for a group performance of 'Roar' by Katy Perry – a nod to the fact Katy was one of the guest performers that night. And, yep, we didn't miss the fact all of them were wearing animal print of some sort!
Who also spotted Louis singing along from the judges' table?!
Next up was a little taste of what could be in store for The X Factor winner in the form of One Direction or, as the show described them, the biggest success story to ever come out of X Factor. The statistics: four million ticket sales, 38 million records worldwide, fastest selling album of 2013… pretty impressive.
Harry Styles, Zayn Malik, Liam Payne, Louis Tomlinson and Niall Horan took to the stage for a performance of the title track from their Midnight Memories album and judging by the insane screams at Wembley we're not the only ones with five crushes…
Katy Perry then took to the stage for a performance of new single, before Gary teamed up with his hero Sir Elton John for a lively performance. It marked Sir Elton's first time on the show.
So that's it for another year! Although with Dancing On Ice and Tom Daley's Splash! both coming up next month we won't be short of reality shows to become addicted to in the New Year…
The X Factor final in pictures:
Copyright: Rex Features Tom Dymond / Thames