Jack Andrew Lowden (born June 2, 1990) is a Scottish actor. Following a four-year stage career, his first major international onscreen success was in the 2016 BBC miniseries War & Peace, which led to starring roles in feature films. Starring as River Cartwright in the Apple TV series Slow Horses since 2020, he has received nominations for a Primetime Emmy Award and a Golden Globe Award.

Lowden starred as Eric Liddell in the 2012 play Chariots of Fire in London. In 2014, he won an Olivier Award and the Ian Charleson Award for his role as Oswald in Richard Eyre's 2013 adaptation of Ibsen's Ghosts.