Horrid Henry is a children's book series by Francesca Simon and illustrated by Tony Ross. It has been adapted for television, film^[1] and theatre.^[2] Horrid Henry is set in the United Kingdom in 1994.

The first Horrid Henry book was written and published in 1994 by Orion Books. Up until 2015, 24 official Horrid Henry titles were published in the series with a special one-off 25th Anniversary book, published in 2019. The series has sold more than 21 million copies worldwide.^[3]

The books are a slice-of-life series featuring the titular Henry, a wildly misbehaved boy who will typically be faced with a problem and then will often retaliate in interesting ways that involve trickery, rule-breaking and elaborate practical jokes. Henry has a younger brother, Perfect Peter, who is the exact opposite.^[4] Almost every character is known by an alliterative nickname (Rude Ralph, Moody Margaret, Brainy Brian, etc.) with a few exceptions e.g. Mum, Dad and Miss Battle-Axe.

The Horrid Henry stories are read on audiobook by the actress Miranda Richardson and published by Orion Audio.

Each title in the main series consists of four short stories with black and white illustrations. The titles The Early Readers series, aimed at younger readers, each consist of a single story with colour illustrations. Each story in that series, except Don't be Horrid Henry!, was originally published in a main series title. Don't be Horrid Henry! is an original story about Henry as a toddler. Eleven fact books, written from Henry's point of view, have also been published along with eight joke books, eleven colour books and at least twelve activity books as well as a series of annuals.

Horrid Henry is published in 25 languages around the world. In April 2009, the US Sourcebooks' Jabberwocky imprint released four Horrid Henry paperbacks nationwide, which included Horrid Henry, Horrid Henry's Stinkbomb, Horrid Henry and the Mega-Mean Time Machine" and Horrid Henry Tricks the Tooth Fairy. Sourcebooks has released additional Horrid Henry titles including activity pages, event kits and a teacher's guide.^[5]

On 23 June 2010, Vertigo Films announced that a live action 3-D film of Horrid Henry was in production. The film's plot focuses on Henry and The Purple Hand Gang fighting to prevent the closure of their school by an evil private school Headmaster.^[6] The film was released on 29 July 2011 in the United Kingdom and 11 January 2013 in Australia.

• In April 2008 "Horrid Henry and the Abominable Snowman" won the Galaxy Children's book of the Year Award.
• Horrid Henry has twice been nominated for BAFTA's Best Animation; in 2009 and 2010.
• On 23 November 2018, the show's official Twitter account posted a GIF of Henry "flossing" which went viral.

• Horrid Henry (TV series)
• Horrible Harry, a different character