Polybius is a 2017 shoot 'em up video game developed and published by Llamasoft. It was released in May 2017 for the PlayStation 4, with PlayStation VR support available. A version for Windows was released in December 2018. The game takes its name and inspiration from the fictitious 1981 arcade game Polybius. It is also inspired by games like TxK and aims to induce the psychological state of flow. It was positively received by critics.

Shoot 'em ups are a sub-genre of action games. There is no consensus as to which design elements compose a shoot 'em up; some restrict the definition to games featuring spacecraft and certain types of character movement, while others allow a broader definition including characters on foot and a variety of perspectives.