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A fresnel prism is a type of compact lens originally developed by French physicist Augustin-Jean Fresnel for lighthouses. The design allows lenses to have large aperture and short focal length without the mass and volume of material required by a lens of conventional design. A fresnel lens can be made much thinner than a comparable conventional lens, in some cases taking the form of a flat sheet. A fresnel lens can capture more oblique light from a light source, allowing thus light from a lighthouse equipped with one to be visible over greater distances.

The special grooves in fresnel prisms can change the way light enters the eye, making them useful in treating blurred or double vision.