We present a holographic authentication tag realizing an optical pseudorandom physical unclonable function (PRPUF). PRPUF provide a high level of security and are practically impossible to clone without the knowledge of a random, secret, “key”. Our PRPUF relies on the speckle pattern of light scattered from a metasurface, serving as a unique “fingerprint”. The metasurface design process constitutes a one-way function, thus preventing counterfeiters from replicating the speckle pattern without access to the initial conditions (the “key”). The metasurface-based PRPUF is robust against fabrication errors and resilient to counterfeiting. Compared to contemporary physical authentication approaches, this solution provides a high certainty level at low cost while requiring simple interrogation apparatus, thus rendering it highly attractive for authentication applications.