Recent experiments show that the impact of a jet of non-cohesive granular particles produces a highly collimated ejecta sheet. The angle of ejection agrees quantitatively with that produced by the impact of a water jet. An analogous behavior, the emergence of highly collimated jet upon oblique impact of two gold ions, has been cited as evidence for the liquid nature of the quark-gluon plasma at RHIC. Both examples share the common feature that a system of particles exhibits a liquid-like collective response even though the particles are not confined together nor experience attraction towards each other. We analyze the impact of two granular jets. The velocity field and stress distribution within the granular jet agree quantitatively with that of a perfect-fluid flow. Our results show that this close correspondence does not require that the system of particles be in a liquid phase possessing a Newtonian viscosity. The only requirements are that the collective motion is approximately incompressible and that the shear stresses within the jet are small relative to the normal stresses.