Siobhan Hewlett (born 15 April 1983) is a British-born Irish film, television, radio and theatre actress, writer, producer, poet and artist.

Her acting credits include Monsieur N (2003), The Canterbury Tales (2003), The Philanthropist (2005), The Virgin Queen (2005), Irina Palm (2007), Torchwood (2008), Hotel Babylon (2009), Henry VIII: The Mind of a Tyrant (2009), Sherlock (2010), Bonded by Blood (2011), Hummingbird (2013), Brakes (2016), The Show (2021), and McDonald & Dodds (2021).

[6] Hewlett made her professional stage debut at The Finborough Theatre in London, starring opposite Chris O'Dowd, Clarke Peters, and Daniela Nardini in Etta Jenks.

[8] In 2005, Hewlett made her West end stage debut at the Donmar Warehouse, starring alongside Simon Russell Beale, in the Christopher Hampton hit play The Philanthropist,[9] To rave reviews, “ The luscious & accomplished Araminta was played by the luscious & accomplished Siobhán Hewlett, whose electrifying stage presence would have stolen any other show.” - The Independent.

[10] In 2007, she starred in the indie hit Irina Palm,[11] opposite Marianne Faithfull and Kevin Bishop which won the audience prize at The Berlin international Film Festival.