Are there any actors or actresses that use their original names?

Warren Beatty almost does.
His original birth name was Henry Warren Beaty. http://en.wikipedia.org/wiki/Warren_Beatty

All of the Barrymores. Ethel, Drew…................

@john65pennington Good call. There’s gotta be more than that. Why do they change their names in the first place? And when they do, is it through the court or do they just decide that it’s changed?

Renee Zellweger, William Mapother, Zach Galifianakis are a few. You couldn’t make up names like those, even if you could, why would you use one as a stage name?

One reason many might change their names is that the Screen Actors Guild requires each registered member to have a unique name. That is why Michael J. Fox had to use a middle initial, there was already a Michael Fox registered with SAG. Fun fact: his actual middle initial is A but he decided to go with J as it didn’t sound quite so conceited!

There are tons. To name a few: Katie Holmes
Andrew McClain
Matt Damon
George Clooney
Julia Roberts

Though Katie is short for Katherine and Matt is short for Matthew, I’m assuming here that you meant significantly different and not common nicknames used by the public.

Clinton Eastwood, Jr.
John Christopher Depp II
Leonardo Wilhelm Dicaprio

Kiefer William Frederick Dempsey George Rufus Sutherland

Benedict Cumberbatch has one of the single coolest names ever.

I’m pretty sure all of the Wilson brothers and all of the Baldwins use their own names.

Marlon Brando was born Marlon Brando, Jr. Director Martin Scorsese said of him, “He is the marker. There’s ‘before Brando’ and ‘after Brando’. Actor Jack Nicholson once said, “When Marlon dies, everybody moves up one.”

And my other hero, Orson Welles, was born (George) Orson Welles.

Madonna was born Madonna (something-or-other)

John Malkovich, born John Gavin Malkovich. Seriously, who would make up such a name? The thing about actors is that they are famous for being OTHERS, not for being themselves, so it kind of makes sense to use a contrived name. Take Tom Cruise for instance. Tom Cruise is the cocky pilot of Top Gun, the confident spy of Mission Impossible, but frankly nobody wants to know more about the twit scientologist who jumps up and down on Oprah’s couch, whose name is Thomas Mapover IV.

My old school-mate used the name Thom in High School, but otherwise, that’s his real name.

In the Hanana Montana movie, Miley Cyrus uses her real name, Miley.

Walter Matthau
Beyoncé Knowles
Jean Reno

Engelbert Humperdinck’s real name is Arnold George Dorsey. How do you pick a name like Engelbert?