Guimoon: The Lightless Door (Korean: 귀문; Hanja: [Gwimun] Error: {{Lang}}: Latn text/non-Latn script subtag mismatch (help)) is a 2021 South Korean horror film, directed by Sim Deok-Geun and starring Kim Kang-woo, Kim So-hye and Lee Jung-hyung. The film is simultaneously produced in 2D, ScreenX and 4DX versions. This is a first time in any Korean film that audience can feel the horror of the characters with screens extended to both walls, and 4DX equipped with motion chairs and special environmental equipment. The film depicts the story of the director of a psychic research institute and college students. It was released in theatres in 2D, ScreenX, and 4DX on August 25, 2021.