This chapter describes the way in which transformation optics can be used to design lens antennas. It begins with a brief introduction to the analytical method and describes the difficulties faced by practical applications, in terms of anisotropic material requirements and bandwidth restrictions. Two further variants of transformation optics are provided to circumvent these issues, which are the quasiconformal transformation technique, and non-Euclidean transformations for surface devices. The use of both these methods results in material property requirements that can be easily implemented with dielectrics. These two techniques are thoroughly described, with the benefits and drawbacks they present detailed. The discussion is supported throughout with a number of application examples in each section, which include planar lenses, bespoke lenses, curved surface wave lenses, and a surface wave cloak. Examples are chosen to illustrate the variety of ways in which transformation optics can be applied to antenna systems, and are all supplemented by simulation or measurement data.