The ability of ground-based global navigation satellite system (GNSS) receivers to detect tropospheric water vapor was demonstrated during the early 1990s. GNSS meteorology comprises three branches: GNSS radio occultation, GNSS reflectrometry, and GNSS ground-based measurements. This chapter begins by providing a historical background of how geodetic study started to implement a strategy for correcting radio signal propagation through the neutral atmosphere. This is followed by an overview of the process used to retrieve tropospheric parameters from geodetic software. Next, the chapter covers the details about the conversion of these GNSS parameters into wet delays and water vapor content. The use of GNSS meteorology for monitoring severe weather is then illustrated, highlighting the interest in very short-range forecasts, called nowcasting. Finally, the chapter presents the future applications and synergy with other techniques using derivative products.