An antenna is a conductor or group of conductors used for radiating electromagnetic energy into space or collecting electromagnetic energy from space. When radio frequency signal has been generated in a transmitter, some means must be used to radiate this signal through space to a receiver. The device that does this job is the antenna. The transmitter signal energy is sent into space by a transmitting antenna and the radio frequency energy is then picked up from space by a receiving antenna. The radio frequency energy that is transmitted into space is in the form of an electromagnetic field. As the electromagnetic field arrives at the receiving antenna, a voltage is induced into the antenna. The radio frequency voltage induced into the receiving antenna is then passed into the receiver. There are many different types of antennas in use today but emphasis is on antennas that operate at microwave frequencies. This chapter discusses the two major types microwave antenna which are the horn-reflector and parabolic dish antennas. In order to satisfy antenna system requirements for microwave propagation and choose a suitable antenna system, microwave design engineers must evaluate properly these antenna properties in order to achieve optimum performance.