The Global Navigation Satellite Systems（GNSSs）

including the United States Global Positioning System（GPS）

Russian GLONASS

the European Union’s Galileo

and China’s Bei Dou

provide L-band microwave signals with high temporal resolution. These systemshave extended the applications of the GNSS from positioning/navigation to remote sensing. Since the 1990 s

the versatile refracted GNSS signals have been successfully demonstrated to sound the ionosphere and troposphere. In the pasttwo decades

reflected signals

which involve making measurements of the reflections from the Earth

have shown theircapacity for earth observations over wateror land.On the basis of such background

GNSS remote sensing

as a hybrid of GNSS and remote sensing

has been developed over the years. The concepts of GNSS remote sensing can be summarized into two categories: GNSS refractometryand GNSS reflectometry（GNSS-R）. The applications of GNSS remote sensing involves atmospheric water vapor

seismo-ionospheric disturbances

oceans

lands

hydrology

and the cryosphere. To further promote the applications of the GNSS remote sensing technology in atmospheric

seismic

and water cycle studies

this review systematically introduces the international and domestic forefront of GNSS remote sensing technology and its applications

with a focus on GNSS/meteorology

GNSS ionospheric seismology

GNSS radio occultation

ocean observations

land applications

cryosphere applications

and missions of GNSS-R. We also discuss and provide an overview of the bottlenecks related to the further development of each branch of GNSS remote sensing. The next generations of GNSS systems

especially GPS III and Bei Dou II

are expected to show improved performance and offer excellentcapabilities to users around the globe. This study can provide references for the future development of GNSS remote sensing technologiesand otherrelated subjects.