They've become household names - but turns out a lot of our favourite stars were born with completely different ones.
Here are the real names of some of the world's most famous celebrities.
1. Elton John
Elton John's real name is Reginald Dwight - he changed it when he entered show business, and added in the middle name Hercules for good measure.
2. Vin Diesel
Vin Diesel came up with his stage name using an anagram of 'I End Lives.' Before that, he was known as Mark Sinclair.
3. Joaquin Phoenix
It's not hard to figure out why Joaquin Phoenix changed his last name. Before he was Phoenix, he was Joaquin Bottom.
4. Whoopi Goldberg
Born Caryn Johnson, Whoopi Goldberg got her name from her lack of shyness about bodily functions. She once explained, "If you get a little gassy, you've got to let it go. So people used to say to me, 'You're like a whoopee cushion'."
5. Marilyn Manson
Marilyn Manson, born Brian Hugh Warner, got his name by combining the first name of an iconic female sex symbol and the last name of an iconic serial killer. Marilyn Monroe and Charles Manson equals Marilyn Manson.
6. Olivia Wilde
Olivia Wilde grew up as Olivia Cockburn, but changed her name in later years after developing a profound respect and admiration for Irish writer Oscar Wilde.
7. Jamie Foxx
It wasn't until Eric Marlon Bishop started doing comedy that he changed his name to Jamie Foxx - and it was because he wanted to be mistaken for a woman. Apparently, female comedians were routinely called to the stage before their male counterparts, and Foxx didn't want to wait.
8. Iggy Azalea
It's no big surprise that Iggy Azalea isn't the Aussie rapper's real name. She was actually born Amethyst Amelia Kelly, but decided to go with a stage moniker comprising of her pet dog's name (Iggy) and the street her family live on (Azalea).