Hit songs you didn’t know were written by other famous artists -

When a song is "by" an artist, the singer typically gets all the credit, though oftentimes they didn’t write it themselves. Pop songs these days tend to be massive collaborations, sometimes with dozens of people involved for just three minutes of music. But beautiful things can happen in such a collaborative environment, like getting major stars to write songs for other major stars, sometimes in completely different genres than their own, and glimpsing how genius can thrive in more than one outlet without the shackles of a so-called brand or image.

Several surprising artists are behind some of pop's biggest tracks, revealing hidden collaborations we would never think to combine. Click through to discover them.

© Getty Images

Bebe Rexha: 'The Monster' by Eminem ft. Rihanna -

Before making it on her own, Rexha penned many songs for bigger stars. She co-wrote the Billboard Hot 100 chart-topper 'The Monster' for Eminem and Rihanna. Her high-reaching vocals are actually used on the track without crediting her!

© Getty Images

Bebe Rexha: 'Like a Champion' by Selena Gomez -

Bebe Rexha also co-wrote 'Like a Champion' for Gomez's album 'Stars Dance,' and she helped out Gomez's ex Nick Jonas write his song 'Under You,' per Billboard.

© Getty Images

Jessie J: 'Party in the USA' by Miley Cyrus -

Jessie J, who is notably not from the USA, famously said that the royalties from penning this hit track, alongside producer Dr. Luke, paid her rent for three years.

© Getty Images

Ryan Tedder: 'Halo' by Beyoncé -

This track was such a massive success and a defining hit for Queen Bey, that it was hard to believe it was the lead singer of OneRepublic, Ryan Tedder, who helped her write it. He also co-wrote her beautiful ballad 'XO.'

© Getty Images

SZA: 'Feelin Myself' by Nicki Minaj and Beyoncé -

Producer Hit-boy revealed SZA was responsible for writing a part of the smash hit and the singer herself confirmed so in an interview with Sway's Universe. “Yeah, I wrote parts of that, a nice chunk of that,” though she couldn't say how it came about. “The call just got put in and then I arrived, I have no idea. Hit-Boy produced and I wrote the lyrics so Nicki and Beyoncé are singing some of the things that I wrote to it.”

© Getty Images

Pharrell: 'Hot In Herre' by Nelly -

Nelly revealed that he'd felt unsatisfied with the final cut of his album 'Nellyville' and brought in Pharrell to help. 'Hot In Herre' was born, with the additional help of Chuck Brown, and the song reigned the Billboard Top 100 for seven consecutive weeks, cementing Nelly's legacy.

© Getty Images

Pharrell: 'Hollaback Girl' by Gwen Stefani -

Pharrell has a legacy of his own, but once you start looking at the songs he has penned, you quickly realize his influence is much, much greater. Gwen Stefani knew to reach out to him when she wanted to write a song in response to Courtney Love derogatorily referring to her as a "cheerleader." Thus, with the help of Pharrell and his co-producer partner Chad Hugo, 'Hollaback Girl' came to fruition.

© Getty Images

Kesha: 'Till the World Ends' by Britney Spears -

Kesha has said that this song “was written specifically for Britney,” she told Digital Spy. “'I put my brain in Britney Spears land and wrote that whole song for her.”

© Getty Images

Taylor Swift: 'You'll Always Find Your Way Back Home' by Miley Cyrus -

Swift is another artist who has a legacy of her own but continues to spread her influence behind the scenes, even using pseudonyms. She penned this country pop song written for the 'Hannah Montana' movie, and later wrote country tracks for artists like Little Big Town ('Better Man'), Sugarland ('Babe'), and Kellie Pickler ('Best Days of Your Life').

© Getty Images

Taylor Swift: 'This Is What You Came For' by Calvin Harris and Rihanna -

Originally written under her pseudonym Nils Sjöberg, Swift and her then-boyfriend Calvin Harris are the sole writers on this hit track. The song also reportedly features Swift's uncredited backing vocals.

© Getty Images

John Legend and Kanye West: 'I Want You' by Janet Jackson -

These two music geniuses have made names for themselves and for others, boosting the already magnificent talents of the likes of Janet Jackson and J. Cole, as well as working on each other's songs like West's 'American Boy' with Estelle and Legend's 'Heaven.'

© Getty Images

Ed Sheeran: 'Love Yourself' by Justin Bieber -

Sheeran worked with Bieber to write this track. He also penned One Direction's 'Little Things,' but that was originally meant for himself until he gave it away to his friend Harry Styles. He later penned '18' for the band as well.

© Getty Images

Ed Sheeran: 'Your Song' by Rita Ora -

Sheeran also often writes for women, and co-wrote this track for Rita Ora with producer Steve Mac, marking Ora's comeback in 2017 and serving as the lead single from her second album, 'Phoenix.'

© Getty Images

Katy Perry: 'I Do Not Hook Up' by Kelly Clarkson -

Katy Perry is another pop star who has co-written a few songs for other stars, including this track by Kelly Clarkson, as well as more surprising ones like 'Get On Your Knees' by Nicki Minaj featuring Ariana Grande.

© Getty Images

Katy Perry: 'That's More Like It' by Selena Gomez & The Scene -

And before Katy Perry had made it as an artist on her own, and back when Selena Gomez was in a band, Perry co-wrote this song with Billy Steinberg and his songwriting partner Josh Alexander.

© Getty Images

Bruno Mars: 'Forget You' by CeeLo Green -

Bruno Mars started writing this song with his Smeezingtons production partner Philip Lawrence, but they weren't sure it was worth completing until CeeLo Green got his hands on it, reports the New York Post, and the rest is history.

© Getty Images

Lady Gaga: 'Elevator' by The Pussycat Dolls -

Before cranking out hit after hit for herself, Lady Gaga penned hits for other stars. Back in 2008, under her non-stage name Stefani Germanotta, she penned this PCD track, according to People.

© Getty Images

Lady Gaga: 'Quicksand' by Britney Spears -

Gaga even wrote a song for none other than Britney Spears, alongside Fernando Garibay, for her sixth album, 'Circus.'

© Getty Images

Harry Styles: 'Just a Little Bit of Your Heart' by Ariana Grande -

Grande herself told MTV she was in the studio recording her album 'My Everything' in 2014, when Harry Styles stopped by. She said her producers asked if he wanted to write a song for her; he said yes, and made this track.

© Getty Images

Mike Posner: 'Don't Tell Me You Love Me' by Big Sean -

The 'Cooler Than Me' singer has written for many artists, including co-writing this track for Big Sean. Posner also co-wrote tracks like 'Boyfriend' for Justin Bieber and 'Sugar' for Maroon 5.

© Getty Images

Drake: 'R.I.P' by Rita Ora -

Under his name Aubrey Graham, Drake co-wrote this track for Rita Ora featuring British rapper Tinie Tempah. Ora herself shot down rumors that Drake initially wrote the song for Rihanna, telling The Sunday Times that she would have fought for it even if it was.

© Getty Images

Sia: 'Diamonds' by Rihanna -

Sia is another figure who has penned many songs for various pop stars throughout her career. She wrote 'Diamonds' for Rihanna, alongside producers Benny Blanco and Stargate.

© Getty Images

Sia: 'Perfume' by Britney Spears -

Sia co-wrote this track for the Princess of Pop. She also worked on Katy Perry's 'Double Rainbow,' Christina Aguilera's 'You Lost Me' and 'Blank Page,' Carly Rae Jepsen's 'Boy Problems,' Kylie Minogue's 'Kiss Me Once,' and numerous other tracks, which Time counted to be a total of 73 in 2016.

© Getty Images

Frank Ocean: '1st & Love' by Brandy -

Long before Frank Ocean became a star himself, he was a songwriter for others—specifically for artists who recognized a genuine talent in him, like Brandy. On her 'Human' album, he helped write '1st & Love' along with 'Locket (Locked in Love),' and on her later 'Two Eleven' album he wrote 'Scared of Beautiful.'

© Getty Images

Frank Ocean: 'I Miss You' by Beyoncé -

Ocean also helped write a track for Beyoncé, who recalled in an interview with Complex: “Jay had a CD playing in the car one Sunday when we were driving to Brooklyn," which was when she first heard Ocean. "I noticed his tone, his arrangements, and his storytelling," she said. "I immediately reached out to him–literally the next morning. I asked him to fly to New York and work on my record."

© Getty Images

James Blake: 'Pray You Catch Me' by Beyoncé -

Though the English musician makes very different music for himself, Blake—who has also written songs with Frank Ocean—co-wrote Beyoncé's album opener 'Pray You Catch Me' for her epic 2016 project 'Lemonade,' as well as the track 'Forward.'

© Getty Images

James Blake: 'Element' by Kendrick Lamar -

On Kendrick Lamar's Pulitzer Prize-winning album 'Damn,' Blake also co-wrote and co-produced the hit single 'Element.'

© Getty Images

Drake: 'Un-Thinkable (I'm Ready)' by Alicia Keys -

Alicia Keys collaborated with Drake to write this song (he was credited as Aubrey Graham), and Drake even has some uncredited background vocals on it.

© Getty Images

Christina Milian: 'Baby' by Justin Bieber -

Christina Milian helped write the song alongside her then-husband The-Dream, Tricky Stewart, and Ludacris, which actually became a point of conflict in Milian and The-Dream's divorce, particularly surrounding the 10% of The-Dream's publishing interest in the track.

Sources: (Billboard) (Digital Spy) (New York Post) (The Sunday Times) (Complex) (Time) (Cosmopolitan) (People) (BuzzFeed)

See also: Songs everyone thinks are by other artists

© Getty Images