The four piece, made up of Jesy Nelson, Perrie Edwards, Jade Thirlwall and Leigh-Anne Pinnock, were put together on the show in Series 8.
They became the first (and still the only girl) group to win the show, mentored by then judge Tulisa.
Their winner's song - a cover of Cannonball - gave the girls their first Number 1.
But their first original hit was Wings which went to the top spot in 2012.
The Official Charts Company reports that the song sold over 100,000 copies in its first week and its sales to date total more than half a million.
The girls join only Alexandra Burke and Leona Lewis in having their first 'proper' single going to Number 1.
And it was far from a fluke with Little Mix going on to enjoy a further two Number 1 tracks, including 2016 smash Shout Out To My Ex.
Overall the group have so far scored a total of 12 top ten singles from their four albums, which have all made the top 5.
Fans of the four piece have been sharing memories on Twitter with the hashtag #7YearsOfLittleMix
One wrote: "These 4 girls had one dream in common and randomly were put in a group but what they didn’t know was they will end up being the biggest girl group of this generation and having the purest friendship, i’m grateful i got to witness this and be part of the dream #7YearsOfLittleMix "
Another added: "It’s been 7 years since these four women got together and have grown right before our eyes. Since day 1 you have inspired and empowered us through your music and through your actions.
"You’re friendship is so precious. I’m so proud of you girls! ♡ @LittleMix #7YearsOfLittleMix "
The celebrations come as Little Mix prepare to drop their fifth studio album.
Confirming a new record was on its way, Leigh-Anne said back in March: "We have a new album coming out this year which is really exciting."
The official Little Mix Twitter then confirmed: "It's official...#LM5 is actually in the works... 😮 We're going to be patiently waiting for this one, it's going to be an absolute dream! 😍 LM HQ x"
Little Mix's new album doesn't have a release date yet but the girls' past four records have all been out in November.
Their new release will be a follow up to Glory Days, which went to Number 1 in 2016 and has since sold almost a million copies, certified three-times platinum.