Interfacing quantum optics with nanotechnology could boost the prospects for the integration of scalable quantum information technologies. Quantum information processing is a key future technology that promises superior communication and computing performance beyond classical information. Any candidate to realize its full potential will require solid-state coherent units with long-range interactions. The most promising approaches rely on photons and spins.Recent demonstrations of the quantized character of surface plasmons – oscillations of electrons bound to photons – have spurred research in miniaturized quantum optics with plasmons, known as quantum plasmonics. Despite the interest, experiments aiming at nanoscale quantum circuits and communication with plasmons are still in their infancy because of the difficult generation of a coherent interaction between different single-plasmon nanosources.Here we propose a conceptually new route to quantum plasmonics that harnesses the properties of quantum materials. These are tunable quantum systems with properties that emerge from the strong interaction between coherent units, with macroscopic states that are determined by collective quantum many-body physics.We will create a unique quantum state: a Bose-Einstein condensate of surface plasmons for which quantum properties become apparent in a many-emitter system. This will allow the construction of a quantum metamaterial, a reconfigurable optical material that exploits coherence.Topological insulators – another fascinating quantum material that is metallic on its surface, insulating in its bulk and locks electronic spin to current direction – will be shown to support plasmons and spin-plasmons (a plasmon travelling with a spin wave). This will bridge spintronics and nanophotonics, the two most promising approaches for integrated quantum information.Both plasmonic quantum materials will be novel resources for classical and quantum nanophotonic devices.