Some of the biggest names in the business don't go by their birth names.
Whether it's for anonymity purposes, or just because a more unique working name leads to more promising career prospects, when it comes to Hollywood, the right name can change everything. It's an actor's brand and reputation, after all!
The following 15 celebrities who tweaked (or downright changed!) their real names will undoubtedly surprise you. Take a look:
1. Julianne Moore
Real name: Julie Smith
When Julianne went to join SAG, she was told that she had to choose a new name, because there was already a Julie Smith on the register. So, how did she come up with another name?
"My dad's name was Peter Moore Smith, and my mother's name was Anne Smith, and I used both their names so I wouldn't hurt anybody's feelings. But it's horrible to change your name. I'd been Julie Smith my whole life, and I didn't want to change it."
And while she now goes by Julianne Moore for business, to her nearest and dearest, she's still 'Julie.' So if you're ever lucky enough to be pals with the Still Alice actress, remember that.
2. Lady Gaga
Real name: Stefani Joanne Angelina Germanotta
It was all down to one music producer, Rob Fusari, who coined the stage name for Gaga that we know today. Apparently, every time the budding singer would walk into the studio, he would always sing 'Radio Ga Ga.' And when a predictive text from Fusari once changed 'radio' to 'lady,' she realized it was her calling.
But before she changed her name in 2006, Gaga recorded an EP under her real name. Here it is:
3. Tom Cruise
Real name: Thomas Cruise Mapother IV
We might know him by the first part of his full name, but Mapother IV is also written on his birth certificate. His father was Thomas Mapother III, so he took on his name.
4. Iggy Azalea
Real name: Amethyst Amelia Kelly
Amethyst is Iggy's real, and equally awesome, name. Back in her teens, when the young Australian moved to America to pursue her dreams of being an entertainer, she took the name of her childhood dog and the street where she grew up and combined them into her stage name.
5. Shania Twain
Real name: Eilleen Regina Edwards
When she was younger, the Canadian singer got her last name from her stepfather. She added 'Shania' herself, a native Ojibwa word that means "on my way."
6. Jamie Foxx
Real name: Eric Bishop
When Eric was a young comedian, he realized that at open mic stand-up nights, women were often called first to perform. So he changed his name to a more androgynous name.
His new surname was a tribute to comedian Redd Foxx.
7. Calvin Harris
Real name: Adam Richard Welles
Taylor Swift's DJ beau is known as Adam to his loved ones. Who'd have thought? And the reason for the name change all comes down to one thing. The musician says:
"I thought Calvin Harris sounded a bit more racially ambiguous. I thought people might not know if I was black or not. After that, I was stuck with it."
8. Demi Moore
Real name: Demetria Gene Guynes
Demetria Gene Guynes became Demi Moore when she married singer Freddy Moore back in 1980. And although he didn't stick around for very long, the name did.
9. Nicki Minaj
Real name: Onika Tanya Maraj
Nicki's real name was quite the mouthful to rap, which is why she went for a shorter, more accessible version.
10. Olivia Wilde
Real name: Olivia Jane Cockburn
When Olivia started acting as a budding blue-eyed, blonde-haired actress, she was known by the surname Cockburn. Naturally, this didn't have the mad sex appeal that she is associated with today.
So in high school, after starring in a play by Oscar Wilde, she changed it to the last name of the Irish author. And this turned out to be very fitting, considering she comes from a family of writers and journalists.
Real name: Michael Ray Nguyen-Stevenson
You didn't think Kylie Jenner's boyfriend was really just called 'Tyga' did you? He actually goes by a more normal 'Michael.'
12. Reese Witherspoon
Real name: Laura Jeanne Reese Witherspoon
Once upon a time, this Southern girl was known as Laura Jeanne. Yet, changing her name to Reese gave her acting career a little bit of a kick.
13. Alison Brie
Real name: Alison Brie Schermerhorn
No, Brie is not her last name. She was actually born with the unique name of Schermerhorn. I'm not even going to attempt to pronounce that!
14. Antonio Banderas
Real name: José Antonio Dominguez Bandera
Antonio Banderas opted for a shorter version of his Spanish full name, tweaking it a little to give it the oomph it needed in Hollywood.
15. Kit Harrington
Real name: Christopher Catesby Harrington
For those of you who don't know, 'Kit' is the traditional nickname for Christopher, which is all-but forgotten in the U.S. When the Game of Thrones star was a kid, he assumed the shorter version of his name and has never looked back since. I wouldn't be surprised if he started a revival of the nickname now though...