Shauna Macdonald (born 26 April 1981) is a Scottish actress. She began her career starring in The Debt Collector (1999). She then had her breakthrough starring as Sam Buxton in the television series Spooks (2003–2004). After departing the series, she starred as Sarah Carter in the horror film The Descent (2005), the role for which she is best known. She gained widespread recognition and praise for her performance, and was nominated for the Saturn Award for Best Actress. The film established Macdonald as a scream queen. She reprised her role in its sequel The Descent Part 2 (2009).

Macdonald has continued having starring roles in horror films, portraying Adelaide in Mutant Chronicles (2008), Kate in Howl (2015), Dana in Nails (2017), and Dr. Elle Chrysler in White Chamber (2018), for which she won the Scottish BAFTA Award for Best Actress. She is also known for her roles as Carole Robertson in the film Filth (2013), Agnes Muncie in the television series In Plain Sight (2016), a pilot in Star Wars: The Last Jedi (2017), and as psychiatrist Dr. Wallace in the critically acclaimed miniseries The Cry (2018). She is the voice of Professor Squawkencluck in the 2015 revival of the 80s animated television series Danger Mouse (2015–present).

Macdonald is the co-artistic director of Edinburgh Youth Theatre in Bellfield and has been since 2014. She also teaches public speaking classes, which she teaches through her own company called If In Doubt Shout.