In this chapter, we focus on the application of plasma structures to realize reconfigurable antennas. Several approaches are presented to dynamically control the beamwidth and radiation gain of circularly polarized helical antennas based on plasma reflectors. Ideas and design principles were discussed and confirmed by full-wave simulations and measurements of realized prototypes. It is shown that plasma reflectors can be effectively used to design reconfigurable helicone antennas with controllable gain and beamwidth. The chapter also presents a reconfigurable slotted antenna using a plasma tube inside the metallic waveguide. It is shown that the radiation pattern of the antenna can be readily reconfigured by changing the state of the plasma column. In short, it is shown that in contrast to conventional methods based on electronic or mechanical devices, reconfigurable antennas based on plasma media benefit from simple and relatively low-cost structures as well as high performance.