The actress has previously appeared in Doctors and is currently performing in the National Theatre’s West End production of The Curious Incident of the Dog in the Night Time.
Doctor Who is her first major television role and Mackie said she was “incredibly excited” to be joining the series.
She added: “It’s such an extraordinary British institution, I couldn’t be prouder to call the TARDIS my home!”
Mackie will star alongside Peter Capaldi in both the Christmas special and next year’s full series which will be the final run overseen by Executive Producer Steven Moffat.
Speaking of her co-star, the actress said: “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.
“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.”
Capaldi commented: “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.”
Steven Moffat, Lead Writer and Executive Producer adds: “A new face in the TARDIS, a new voyage about to begin: welcome aboard the amazing Pearl Mackie! This is where the story really starts.”