This book highlights the maritime applications of Global Navigation Satellite Systems (GNSSs) with emphasis on BeiDou Navigation Satellite System (BDS). The book systematically summarizes the technical standards for maritime applications of GNSS issued by the International Maritime Organization (IMO), the International Telecommunication Union (ITU), and other relevant international organizations. It covers the development history and future prospects of the international standardization of BDS' maritime applications. Various applications of BDS in maritime navigation, including the radio determination service system, the global maritime distress and safety system, the automatic identification system, the vessel monitoring system, the long-range identification and tracking system, and the maritime ground-based augmentation system, are introduced. Promising new directions are put forward. This book is intended for technical engineers in maritime communication and navigation. It is also a valuable reference for researchers, graduate students, and upper-level undergraduate students in maritime-related majors.