Polybius is an urban legend concerning a fictitious 1981 arcade game. The legend describes the game as part of a government-run crowdsourced psychology experiment based in Portland, Oregon. Gameplay supposedly produced intense psychoactive and addictive effects in the player. These few publicly staged arcade machines were said to have been visited periodically by men in black for the purpose of data-mining the machines and analyzing these effects. Allegedly, all of these Polybius arcade machines disappeared from the arcade market.
The urban legend has persisted as a topic of interest for video games journalism and through continued interest, it has served as inspiration for free and commercial video games by the same name.