A vast array of ocean instrumentation has been developed for research purposes since the middle of the twentieth century, among which remote sensing technologies have become increasingly important. Within this class of instruments, high frequency (HF) surface and skywave radar, microwave marine radar and global navigation satellite systems (GNSS)-based radar have been successfully implemented in gathering information on large tracts of the ocean surface. This book provides a systematic introduction to the principles, state-of-the-art methods and applications of HF surface and sky wave radar, microwave marine radar and GNSS-based radar, as well as an exploration of ongoing challenges in the field. Ocean Remote Sensing Technologies: High frequency, marine and GNSS-based radar includes 23 chapters that are organized into three parts, mainly according to sensor types. The first part covers work related to HF radar, the second focusses on microwave marine radar, and the third concentrates on GNSS-based radar. Each part consists of an introductory chapter that provides an overview of the corresponding sensor, followed by chapters focussing on fundamental theory, specific applications, or advanced algorithm development. Each of the chapters is self-contained and readers should be aware that there may be across-chapter differences in symbols used for various parameters. The book is intended for a variety of readers in the radar and remotes sensing communities, and content has been selected with a range of interests and backgrounds in mind.