Being one of the fundamentals of electrical engineering, an antenna is a metallic shape structured to transmit or receive electromagnetic waves. Thanks to the recent advances in nano fabrication and nano imaging, metallic structures can be defined with sizes smaller to that of visible light, wavelengths of several nanometers. This opens up the possibility of the engineering of antennas working at optical wavelengths. Nanoantennas could be thought of optical wavelength equivalent of common antennas. Today physics, chemistry, material science and biology use optical nanoantennas to control light waves. Optical nanoantennas are tailored for many technological applications that include generation, manipulation and detection of light. The near field enhancement of resonant optical nanoantennas at specific wavelengths is their most promising advantage that attracts technological applications. In this thesis, we study the resonance characteristics of optical nanoantennas and investigate the governing factors by numerical calculations. We also evaluate radiated electric field from the resonating nanoantenna. Finally, we employ the resonant near field enhancement in optical nonlinear generation. The fabrication of nanoantennas with FIB milling is also explored.