Recent years have witnessed a tremendous progress in nanofabrication, as well as in the theoretical and experimental understanding of light–matter interaction at the nanoscale. The field of nano-optics has thrived during these times and one of the most exciting related advances in this area has been the concept, design and application of optical antennas, or nanoantennas. Starting within the onset of field-enhanced spectroscopy and near-field optics, the concept has rapidly evolved into a sophisticated tool to enhance and direct spontaneous emission from quantum light sources, boost light–matter interaction and optical nonlinearities at the nanoscale, as well as implement realistic optical communication links. The amount of research activity on optical antennas has grown very rapidly in the last few years, and currently spans a broad range of areas, including optics, physics, chemistry, electrical engineering, biology and medicine, to cite a few. The rapid progress and inherent multidisciplinarity of nanoantennas have produced a situation in which the involved research communities do not necessarily speak the same language. If electrical engineers have an established formalism based on circuit and radiation concepts developed over decades of antenna engineering and design, in optics, physics or chemistry many of the same phenomena are described in very different terms. It is exactly this interdisciplinarity, however, that may lead to groundbreaking findings and applications in a variety of fields of modern science.