An anti-siphoning fuel system that includes a fuel inlet, a fuel tank, at least one fill tube or hose connecting the fuel inlet to the fuel tank such that fuel may flow from the fuel inlet to the fuel tank, and an anti-siphoning element or device coupled to the fill tube or hose that may be installed in existing boats or cars and obstructs a siphoning hose inserted in to the fill tube or hose from entering the fuel tank.