Radar is an object‐detection system that transmits/receives and processes reflected electromagnetic waves to determine the location, angle, and velocity of targets such as aircraft, spacecraft, guided missiles, motor vehicles, and ships. In the radar system, the antenna is an essential component and plays an important role in detecting objects. There are various antenna candidates that can be adopted into radar systems. In this article, definitions of fundamental antenna parameters are given, and then various possible antenna candidates for radar systems are demonstrated and analyzed. Various reflectors with corresponding feeding source have been widely used as radar antennas with high gain and low cost, while phased‐arrays provide the radar system with the ability of dynamic scanning with a flat profile. Combing the advantages of the reflector and the phased array, the concept of reflectarray is introduced and the corresponding design principles and characteristics are discussed. Different types of radiation elements with corresponding characteristics for constructing reflectarrays are presented. Due to the innovative enhancement that novel metamaterials can provide to antenna engineering, radar antennas based on (or incorporating) metamaterials are also presented. In addition, for each antenna type representative examples are demonstrated for a more comprehensive understanding.