A blowout preventer (BOP) is a large valve or series of valves designed to prevent the uncontrolled release of oil, gas, or other substances from a well in the event of a blowout. It is an essential safety device used in oil and gas drilling operations to control the pressure and prevent accidents. The blowout preventer sits on top of the wellhead and can be activated manually or automatically to seal the wellbore and prevent the release of high-pressure hydrocarbons.