Switches are used in RF technology to route the output signal of a power amplifier to different paths, to connect an antenna to different transmit (TX) and receive (RX) branches. RF-switches are also found in modulators and switchable phase shifters. In measurement and production technology, RF switches are used to measure a measurement object using various devices. This chapter presents the most frequently used RF switches. The electromechanical switches, including MEMS, are presented first. Electronic switches, particularly those based on PIN diodes, are discussed in much greater detail below. Of course, the transistor switches are also presented. New are switch architectures that are based on a mode blocker structure of the M parameter circuit technology.