Surface plasmon polaritons, combined excitations of light and free electrons of a metal, have emerged as an alternative information carrier for nanoscale circuitry due to their ability to confine light far below the size of the wavelength. They hold the potential to act as a revolutionary bridge between current diffraction-limited microphotonics and bandwidth-limited nanoelectronics. Interestingly, the nanoscale confinement achievable by plasmons also increases the interaction with quantum emitters, paving the way for quantum applications. Exotic non-classical properties of light such as entanglement and squeezing can be embedded into plasmons and faithfully transmitted and received. Recently, it was also shown that unique coupled plasmonic excitations can be engineered on the nanoscale with artificial media (metamaterials) to enhance and control light-matter interaction. A major departure from the conventional classical description of the plasmon is under development. The aim is to incorporate the “wave” nature of matter manifested in ultra-small metallic nanoparticles and the “particle” nature of light, which can play a role in future integrated circuits with capabilities of quantum information processing. This article reviews developments in the field of quantum nanophotonics, an exciting frontier of plasmonic applications ranging from single photon sources and quantum information transfer to single molecule sensing.