The actress and singer has joined the cast as the Doctor's new companion after months of speculation from the show's loyal fans.
Londoner Pearl, who most recently starred in the stage version of The Curious Incident of the Dog in the Night Time, will play Bill alongside Peter Capaldi's Twelfth Doctor.
Coincidentally, Pearl has only appeared in one other BBC programme before - the medical drama series Doctors!
Pearl's exciting news was announced on BBC1 during half time of the FA Cup semi-final match between Everton and Manchester United.
She replaces Jenna-Louise Coleman, whose character Clara Oswald left the show in 2015.
Jenna left to take on the role of Queen Victoria in a major ITV drama series.
Filming for the next series of the popular sci-fi show will start this year and air in 2017.
In a statement, Pearl says of her new role: "I'm incredibly excited to be joining the Doctor Who family. It's such an extraordinary British institution, I couldn't be prouder to call the TARDIS my home!
"Peter Capaldi is such a brilliant actor, and his Doctor is such a wacky and wonderful character, I can't wait to see what adventures are in store for him and Bill throughout time and space."
She went on to say: "Reading the script at the audition I thought Bill was wicked. Fantastically written, cool, strong, sharp, a little bit vulnerable with a bit of geekiness thrown in - I can't wait to bring her to life, and to see how she develops through the series."
Meanwhile, Peter said: "It is a genuine delight to welcome Pearl Mackie to Doctor Who. A fine, fine actress with a wonderful zest and charm, she's a refreshing addition to the TARDIS and will bring a universe of exciting new possibilities to The Doctor's adventures."
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