The review is devoted to one of the most rapidly developing area of modern optics — optical nanoantennas. Been formulated a general concept of optical nanoantennas and main characteristics that are relevant to this science direction. Accordingly to our classification two main groups of nanoantennas — metal and dielectric (including semiconductors) — are defined. For both groups a literature review is performed. An overview of non-linear optical nanoantennas is provides. Main practical application of nanoantennas and their perspectives are discussed.