Fingerprinting refers to a class of techniques to distinguish products using their unique features originated during production. Fingerprinting has a wide range of applications including supply-chain integrity and device authentication. The authors propose the first fingerprinting technique of light-emitting diode (LED), which is pervasively used in electronics products. The key idea is to use spectral features of LEDs obtained by a spectrometer. Combined with a machine-learning classifier, the proposed method successfully distinguishes ten individual LED samples from the same lot at 99% accuracy.