- HD 1080
- Runtime: 123m.
- Status: Released
- 4
- Languages: en
- Country: Belgium, Germany, France, Romania, United Kingdom
- Director: Tommy Wirkola
- Stars: Noomi Rapace, Glenn Close, Willem Dafoe, Marwan Kenzari, Christian Rubeck
- keywords: chase, dystopia, investigation, fake identity, overpopulation, betrayal, conspiracy, execution, alternative reality, population control, secrecy, septuplets, 2070s, suspenseful, intense, authoritarian
- Production_studio: Nexus Factory, Vendôme Pictures, Raffaella Productions, SND, Title Media, uMedia, uFund
- Slogan: Seven sisters. One identity.
- providers: Netflix, Netflix basic with Ads
- The What Happened to Monday is featured in the top rankings of 2017
- #34 in Top Action Movies of 2017
- #34 in Top Thriller Movies of 2017
- #15 in Top Mystery Movies of 2017
In a world where families are limited to one child due to overpopulation, a set of identical septuplets must avoid being put to a long sleep by the government and dangerous infighting while investigating the disappearance of one of their own.