Kelly Macdonald (born 23 February 1976) is a Scottish actress.

Macdonald is best known for her roles in the films Trainspotting (1996), Gosford Park (2001), Intermission (2003), Nanny McPhee (2005), Harry Potter and the Deathly Hallows – Part 2 (2011), and Brave (2012). For the 2005 TV film The Girl in the Cafe, she was nominated for a Golden Globe and won the Emmy Award for Outstanding Supporting Actress in a Miniseries or Movie. In 2003, she appeared in the acclaimed BBC miniseries State of Play as journalist Della Smith.

For her role in the 2007 film No Country for Old Men, she was nominated for the BAFTA Award for Best Actress in a Supporting Role. She went on to star for five seasons in the HBO series Boardwalk Empire (2010–2014) as Margaret Thompson, for which she received a 2011 Emmy Award nomination.