A trapdoor is a door set into a floor or ceiling.

Trapdoor or Trap Door may also refer to:

• Trap Door (magazine), a science fiction fanzine

The Trap Door, a British animated TV series

• The Trap Door (video game), a computer game based on the animated series

• Trapdoor (software), a piece of computer software used for network administration

• Trapdoor (company), a video game developer

• Trapdoor function, a type of mathematical function used in cryptography

• "Trapdoor", in computing, an outdated synonym for "backdoor", a method used to circumvent normal authorization

• "Trap Door" Springfield, a single-shot breechloading rifle designed and produced at Springfield Armory during the late 19th century

• Trapdoor spider, a spider

• Trap Door Spiders, a literary society

• Trapdoor mechanism for breech loading rifles

Music

• Trap Door (EP), an EP by T-Bone Burnett, or the title song

• "Trap Door", a song by Joey Badass from his album Summer Knights

• "Trapdoor", a song by King Gizzard & the Lizard Wizard from their album Paper Mâché Dream Balloon

• "Trap Door", a song by OneRepublic from their album Waking Up

• "Trap Door", a song by Ozzy Osbourne from Black Rain

• "Trapdoor", a song by Twenty One Pilots from their self-titled album