The stars who've been promoting Justin Bieber's new track What Do You Mean

Justin Bieber

He hasn't released any new music since 2012 - and he's had a slightly bumpy ride over the past couple of years.

But now Justin Bieber's got something to celebrate, with the release of his fourth studio album What Do You Mean?

It's already been leaked, but the Canadian star won't be too bothered.

He's had some pretty heavyweight backers during his #30Days campaign to count down to the release.

It all started when he first revealed he was releasing new music during an interview with Ryan Seacrest in America.

Then it was model Ruby Rose's turn followed by the UK's most famous talk show host, James Corden.

Then it was Mariah Carey, J Balvin and with 25 days left - Kylie Jenner.

Shaq, Travis Scott, Ashley Benson, some random farmers the singer met at a radio station and then with 22 days left it was the turn of Ariana Grande.

Halsey then ushered in day 20 before it was the turn of Big Sean and some Brit stars - like Little Mix...

...and of course - Ed Sheeran wrote a song for his spot.

Then we had US singer Madison Beer and with 16 Days to go - it was third place finishers X Factor USA - Fifth Harmony - with their own little - well - harmony.

With 15 days to wait, it was Meghan Trainor...

Then we had country star Luke Bryan, South Korea's CL and with 13 days to go Bieber ramped it up.

There were three people that day - Christina Perri, skateboard legend Tony Hawk and then this fella...

Then we had actress Hilary Duff, Twenty One Pilots, Tori Kelly and skateboarder Ryan Sheckler ushering in the final 10 days.

Colombian-American actor John Leguizamo was next with US pop group Jack & Jack, Ashton Kutcher, country music duo Dan + Shay, Ellen DeGeneres, Doug the Pug and model Xenia Deli.

Then it was torrent of stars for the final week including fellow Canuck Carly Rae Jepsen, Chris Martin from Coldplay, South Korean rapper G-Dragon, US radio host Elvis Duran and this chap...

With five days it was Joel Houston, Ben Stiller and this young lady...

Four days to go and it was Jason Derulo, country music stars Little Big Town, Larry King, Kate Hudson, Skrillex, Cody Simpson, Mark Wahlberg, basketball player Chris Paul and this famous Canadian...

So on Wednesday it was country duo Florida Georgia Line, Jaden Smith, Steven Tyler from Aerosmith, Todrick Hall and Kevin Hart.

Then...

We then had Alec Baldwin and Martha Stewart before Britney Spears did her bit from Las Vegas...

And that was it - a whirlwind month of singers and celebrities all leading up to this song.

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