Hey Arnold! is an American animated sitcom created by Craig Bartlett for Nickelodeon. It originally aired from October 7, 1996, to June 8, 2004. The show centers on fourth grader Arnold Shortman, who lives with his grandparents in an inner-city tenement in the fictional city of Hillwood. Episodes center on his experiences navigating urban life while dealing with the zany hijinks he and his friends encounter. Many episodes, however, focus on other characters, including major, secondary, supporting, and even minor characters.

Bartlett's idea for the show is based on a minor character named Arnold whom he created while working on Pee-wee's Playhouse. The executives enjoyed the character, and Bartlett completed the cast and setting by drawing inspiration from people and locations he grew up with in Seattle, Washington; Portland, Oregon; and Brooklyn, New York. Bartlett created the pilot episode in his living room in 1994 and official production began in 1995. The animators worked to transform Arnold from clay animation to cel animation, leading to the series premiere in 1996. Hey Arnold! was the final series to be green lit (along with Kablam!) under the leadership of network president Geraldine Laybourne. Production on the show concluded on December 7, 2001, after 5 seasons and 100 episodes. Its last episode aired unannounced on June 8, 2004. A feature film based on the series, Hey Arnold!: The Movie, was released in theaters on June 28, 2002. All five seasons have been released on DVD.

On March 2, 2016, a television film continuation of the series, Hey Arnold!: The Jungle Movie, was greenlit. It picks up from where the series ended and resolved unanswered plotlines of the story. The film premiered on November 24, 2017, on Nickelodeon, Nicktoons Network, TeenNick, NickRewind and on November 24, 2018 as an international theatrical release, wrapping up the series' storyline.