The development of miniaturized non-reciprocal microwave technologies compatible with integrated circuit architectures remains a critical challenge for modern information technology. Here, we present the first experimental characterization of a micron-sized prototypical magnon circulator. Taking advantage of the chiral excitation of spin-waves via nanowire gratings, we propose an original design of a circulator involving three channels of rectilinear and unidirectional spin-wave beams. We demonstrate via a full 3-port spin-wave spectroscopy a genuine spin-wave circulation between the three ports. The narrow frequency band of operation can be tuned over a broad range of frequencies (2 - 8 GHz) with both an external field of up to 100 mT, and the dimensions of the grating specifying the wavevectors. This proposed scheme opens up possibilities for new architectures of integrated and miniaturized non-reciprocal microwave devices.