A photoreceptor cell is a specialized type of nerve cell that is sensitive to light and that sends signals to other neurons by a change in its membrane potential when it absorbs photons. This information is subsequently used by the brain to form a representation of the visual world. In the retina of the vertebrate eye are found two types of photoreceptor cells: rod cells and cone cells.

In plants, photoreceptors are light-detectors containing the blue-green pigment phytochrome. They are involved in many plant processes, such as seed germination, flowering, and leaf fall.