We propose a novel Physical Unclonable Function (PUF) concept based on a single spiking neuron. The inherent variability of the neuron results in a chip-unique analog spiking pattern that is digitized to produce a chip-unique digital key. A stability booster is also employed based on self-masking to obtain a fully stable digital key. The PUF is area and power effective since a single PUF cell is used to produce an arbitrarily sized digital key. We demonstrate PUF quality metrics close to ideal values and argue that the PUF is resilient against various physical attacks.