Theodore John "Theo" Stevenson (born 27 February 1998) is an English actor known for starring as the title character in Horrid Henry: The Movie. More recently he is better known for playing Craig in the family sitcom Millie Inbetween and Toby in the sci-fi drama Humans.
In 2007, Stevenson became an actor and took his first film role in Fred Claus as Young Nicolaus. He then appeared in the black comedy In Bruges in 2008. In 2010 he starred in Reuniting the Rubins where he played the role of Jake Rubins. In 2011 he took on his best-known role as Horrid Henry in Horrid Henry: The Movie where he worked alongside Tyger Drew-Honey and Anjelica Huston. He also appeared in the film's music video and appeared on Daybreak in late 2011.
A year after Horrid Henry: The Movie, Vertigo Films announced that Stevenson would star in an upcoming secondary school version of Streetdance called Streetdance Juniors which was renamed All Stars in June 2012, releasing on 3 May 2013. He stars alongside Akai Osei, Ashley Jensen, Kimberley Walsh and John Barrowman amongst others.