Magnons – quanta of spin waves – propagating in magnetic materials having nano-scale wavelengths and carrying information in the form of a spin angular momentum, can be used as data carriers in next-generation nano-sized low-loss information processing systems. The low losses of magnonic systems can be reached due to the absence of translational electron motion associated with Joule heat-ing and extremely low magnetic damping in the dielectric Yttrium-Iron-Garnet (YIG) material used.The recent revolutionary progress in the growth of high-quality YIG films with nanometer thickness, and in the patterning of these films, opened a way to the practical development of nano-scale mag-nonic computing systems. However, the decrease in sizes of YIG structures to sub-100 nm requires the development of the physical knowledge base for understanding linear and nonlinear magnetization dynamics in nanostructures.The strategic goal of the proposed MagnonCircuits research program is to make a transformative change in the data processing paradigm from traditional electronics to magnon spintronics. The ingre-dients required for such a transformation and addressed by MagnonCircuits are: (i) The fabrication of magnon conduits of sub-100 nm width, the development of a toolbox enabling excitation and de-tection of fast exchange magnons, and the understanding of the physics underlying magnon dynamics at the nano-scale in the exchange interaction regime. (ii) Employment of such novel physical phenom-ena as spin pumping, spin transfer torque and spin Hall effect to overcome the fundamental limita-tions of the state-of-the-art approaches in magnon spintronics, and to compensate the dissipation in magnonic circuits. (iii) Realization of two-dimensional magnonic circuits required for transport and processing of magnon-carried data. A proof-of-concept models of two nano-scale devices – majority gate and magnon transistor – will be developed in the course of MagnonCircuits.