The Russian Sleep Experiment is a popular urban legend and creepypasta story about a secret Soviet-era experiment in which researchers kept prisoners awake for 15 days using an experimental gas. As the story goes, the sleep deprivation caused the subjects to exhibit extreme psychosis, self-mutilation, and violent behavior, ultimately transforming them into grotesque, inhuman figures. Though widely circulated online as a horror tale, there is no evidence to suggest that the Russian Sleep Experiment actually occurred, and it remains a fictional account designed to evoke fear.