And, forgive us slipping into X Factor clichés, but what a journey they’ve been on in that time.
From five baby-faced young singers, the band went on to become one of the biggest pop acts of the decade, topping the charts on both sides of the Atlantic, touring all over the world and making household names out of members Harry Styles, Liam Payne, Louis Tomlinson, Niall Horan and Zayn Malik.
We don’t know about you, but the anniversary has got us feeling all kinds of nostalgic, so let’s take a look back at 1D’s incredible story in pictures, starting at the very beginning...
As we all know, One Direction actually all intended to appear on the X Factor as solo acts, so each of them auditioned individually. Here’s a 16-year-old Harry already charming everyone with his version of Isn’t She Lovely.
Two years on from his first try at The X Factor, 16-year-old Liam Payne powered his way through Michael Bublé’s Cry Me A River, winning over all of the judges (including Cheryl Cole, with whom he would go on to have a child seven years later).
Louis’ audition didn’t actually air on the main show, but after seemingly spending the whole morning straightening his hair, he got a yes from each of the judges.
Similarly, Zayn – or Zain as he was then known – only had his audition shown on The Xtra Factor, rather than the main show. He performed a cover of Let Me Love You by Mario.
Niall was the only one of the 1D boys who didn’t quite nail his audition. Guest judge Katy Perry told him to potentially audition a few years later, while Simon Cowell told him he was underprepared and had oversold his talent. Still, he managed to win a spot at boot camp, where One Direction was formed.
After failing to impress with their dance abilities, the five members of One Direction were given a “lifeline” when they were put together as a group.
Their first performance together as a cover of Natalie Imbruglia’s Torn, which they performed at Simon Cowell’s house, although their chances were almost scuppered after Louis was stung by a sea urchin and had to be rushed to hospital.
As we know, though, the group managed to make it to live shows, where they quickly made an impression on the British public.
Highlights included this Halloween performance...
...and this rendition of Kids In America (during what was supposed to have been “American anthems” week, but we’ll let them off for covering a British singer since it’s them).
You may recall there were also a lot of onesies about during this period.
The band did a great job on X Factor, managing to avoid the bottom two every single week and making it all the way to the final, where they duetted with Robbie Williams (almost a decade later, Louis would join Robbie on the X Factor judging panel, alongside the singer’s wife, Ayda Field).
Ultimately, it was Matt Cardle who the public chose as their winner, but Simon Cowell clearly saw something in 1D, and signed them to his label after the series ended.
The following summer, One Direction unveiled their debut single What Makes You Beautiful, and they went on the promo offensive.
This included a performance on Simon Cowell’s ill-fated series Red Or Black...
...celebrating Niall’s 18th birthday first thing in the morning on the now-defunct Daybreak...
...and, of course, cosying up to Rustie Lee in the This Morning kitchen.
Ultimately their hard work paid off, and they were rewarded with their first UK number one.
And what better way to celebrate than with a massive food fight at G-A-Y, right?
Soon afterwards, the group released their first album, Up All Night, which reached number two in the UK and spawned singles One Thing and Gotta Be You.
To promote the album, they also embarked on their first headlining tour, performing in theatres and small venues around the UK.
Capitalising on their popularity, a range of dolls was also released and as you can see, the quality of the resemlance differed quite drastically from member to member...
This was around the time things really began to blow up for 1D, beginning with their first ever Brit Award win, for Best British Single.
As their profile began to grow on the other side of the Atlantic, US, Australia and New Zealand dates were added to the Up All Night tour, including a handful of area shows.
They also made their debut on Saturday Night Live, where there was apparently an unlimited chinos budget.
Back on their home turf, the group were invited to perform What Makes You Beautiful during the 2012 London Olympics closing ceremony, where they were one of the newest acts on the line-up of mostly British performers.
That year, One Direction also made their VMAs debut, performing One Thing during the ceremony, where they were flanked by their devoted fans.
One Direction scooped all three of the awards they were nominated for that night, including Best New Artist, making them the biggest winners of the night (sidenote: remember Zayn’s blond fringe? Dreamy).
As a nice end to what had been a mammoth year for the group, they also headlined a sold-out show at Madison Square Garden in New York. Even more excitingly, it seemed they were finally ready to put the chinos behind them.
Continuing their global domination, 1D began 2013 by arriving in Japan, posing for this photo (judging from Zayn’s face) roughly five minutes after getting off their long haul flight.
The band looked back on their world travels in the music video for their Comic Relief single One Way Or Another (Teenage Kicks), which included this choice cameo from then-PM David Cameron.
As well as performing the song at the Brit Awards, One Direction picked up the first ever Global Success prize during the ceremony.
The category was a divisive one, as some felt it had only been introduced so 1D could win an award, after losing the British Group title to Mumford & Sons.
The Take Me Home tour, in support of One Direction’s second album, would take them all over the world, and kept them busy for much of the year.
Fortunately, they were able to take some time out so they could be immortalised in wax at Madame Tussauds, gifting us this photo of Harry with what seems to be an enormous pair of tweezers up his nose.
The figures were eventually unveiled in mid-2013. See if you can tell who’s made of wax in the photo above...
One Direction also underwent some pretty impressive transformations for the music video for Best Song Ever, the lead single from their third album, Midnight Memories. Zayn’s was our favourite, obv.
The music video was interspersed with clips from This Is Us, One Direction’s 3D concert film, which people were doing a lot of back in 2013.
The film’s London premiere was also where Zayn and then-fiancée Perrie Edwards revealed to the world that they were engaged. Zayn and Perrie eventually split in 2015.
This year’s VMAs was another biggie for One Direction, who won Song Of The Summer for Best Song Ever (although admittedly it was also the year that Miley Cyrus twerked on Robin Thicke wearing a nude leotard and a foam finger, so we’ll forgive you for forgetting that).
It seemed the tide was beginning to turn, though, and 1D were actually booed by some audience members when they picked up the award, sparking the wrath of Lady Gaga at the time.
The end of the year saw One Direction releasing their third album, Midnight Memories, showcasing a more mature and instrument-driven sound.
To promote the release, the band took part in a seven-hour live-stream, which was all kinds of chaotic, but fans obviously loved it.
The stream featured a cameo appearance from Simon Cowell and Liam learning to wrestle (which is why he’s dressed like that, btw).
There was also this musical number...
...and even an interview with Piers Morgan, for some reason.
Most of 2014 was devoted to – you guessed it – another world tour. This time around, though, One Direction played only at stadiums for the first time.
It was also a good time to watch Harry’s hair get longer...
...and longer again (and yes, that’s Courtney Love he’s cosying up to).
Still, let’s not overlook 2014′s finest One Direction hair moment...
...the Zayn strand. What a time to be alive.
After the release of their fourth album – the imaginatively-titled Four – One Direction embarked on their On The Road Again tour, their fifth in as many years.
Life in the band was clearly beginning to get to band member Zayn Malik, who dropped out of the tour due to stress in March 2015, announcing a week later that he’d quit the band completely.
A few weeks later, Zayn made his first red carpet appearance since leaving the band, walking the red carpet at the Asian Awards in London with his mum as his guest.
He also debuted a new buzzed hairstyle, and while we were sad to see the end of the Zayn strand, we can’t pretend we weren’t loving this style too.
Meanwhile, the rest of the band announced that they would be continuing One Direction as a four-piece following Zayn’s departure. Louis was apparently determined to make every red carpet a fun-filled one in their former bandmate’s absence.
This included continuing the rest of the On The Road Again tour, all the while secretly recording their fifth – and, so far, final – album Made In The A.M.
Anyone who worried how 1D would fare without Zayn needn’t have, though. Their first post-Malik single Drag Me Down – which saw the band playing astronauts in the accompanying music video – topped the singles chart here in the UK.
By the end of the year, it had been announced that One Direction were heading towards a hiatus, but before they hung up their chinos and hairspray, they had to return to their own stomping ground for one last performance.
A few weeks later, they marked their last TV performance as a group, during Dick Clark’s New Year’s Rockin’ Eve.
The beginning of the new year was an especially exciting one for Louis, who celebrated the arrival of his baby son, Freddie, by tweeting this photo, alongside the message: “Meet my little lad, Freddie.”
That same month, the band unveiled the music video for their last single, History, which interspersed clips from their six years in the spotlight, as well as a poignant farewell scene at the very end.
Although One Direction’s hiatus was only supposed to last around 18 months, the band are yet to reunite, with each of them enjoying varying levels of solo success.
And so, let’s reminisce together with a bit of help from the History music video: