We propose a method of optical data storage that exploits the small dimensions of metallic nano-particles and/or nano-structures to achieve high storage densities. The resonant behavior of these particles (both individual and in small clusters) in the presence of ultraviolet, visible, and near-infrared light may be used to retrieve pre-recorded information by far-field spectroscopic optical detection. In plasmonic data storage, a femtosecond laser pulse is focused to a diffraction-limited spot over a small region of an optical disk containing metallic nano-structures. The digital information stored in each bit-cell modifies the spectrum of the femtosecond light pulse, which is subsequently detected in transmission (or reflection) using an optical spectrum analyzer. We present theoretical as well as preliminary experimental results that confirm the potential of plasmonic nano-structures for high-density optical storage applications.