This book combines, for the first time, the topics of radar polarimetry and interferometry. This combination was first developed in 1997 and has since become a major topic in radar sciences and their applications, in particular to space sciences. In its simplest form it concerns the study of interferograms formed by combining waves with different polarisations and their exploitation to infer important physical properties of the planetary surface being investigated. The book is written in three main sections. The first four chapters provide a detailed coverage of all major topics of polarimetry, including its basis in electromagnetic scattering theory, decomposition theorems, and a detailed analysis of the entropy/alpha approach. The next chapter offers a brief introduction to radar interferometry, before developing in three chapters the important new topic of polarimetric interferometry. In this way the book provides a complete treatment of the subject, suitable for those working in interferometry who wish to know about polarimetry, or vice versa, as well as those new to the topic who are looking for a one-stop comprehensive treatment of the subject. The emphasis throughout is on the application of these techniques to remote sensing, and the book concludes with a set of practical examples to illustrate the theoretical ideas.