Global mountainous areas account for about 24 percent of the total global terrestrial area. The mountain area in China makes up approximately 65 percent of the national land area. Thus

China can be described as a mountainous country. Mountains are an important resource foundation and are a vital ecological defense for the existence and development of human beings. However

because of the special energy gradients

mountainous regions are centralized areas for the development of natural hazards. Besides

mountainous areas also serve as a sensitive indicator for global change studies because of their vertical environment gradient. Mountainous areas has become a hotspot and area of focus for many earth system studies. Remote sensing is one of the most important and effective tools for mountain studies. It can provide continuous spatio-temporal land cover

feature status

and historical change information. However

given the dramatically different geometric characteristics of mountainous surface and the various special ecosystem structures and functions

remote sensing applications in mountainous areas still face many challenges and difficulties

including serious geometric and radiometric distortion problems

more complex energy balance process

and more prominent ill-condition retrieving problem for ecosystem parameters than that of the plain area.Mountain remote sensing

which mainly focuses on the basic theories

methodologies

and integrated applications of remote sensing in mountainous environments

is a research branch of the remote sensing science. Although the word "mountain remote sensing" firstly began to be used in the middle 1980 s

the research on remote sensing in mountainous areas can be tracked back to nearly 100 years ago because topographic mapping began early in the photogrammetry remote sensing field. In recent decades

issues regarding the basic theories and integrative applications of mountain remote sensing have attracted worldwide attention. Mountain remote sensing has become one of the most popular research areas in remote sensing sciences. We summarized the scientific significance and several frontier issues in mountain remote sensing studies. Currently

the main contents of mountain remote sensing research should include but not be limited to the following aspects:（1） the interaction mechanism and modeling theory between electromagnetic signatures and mountain land surfaces;（2）spatial–temporal–spectral normalization methodologies for mountainous remote sensing data;（3） remote sensing modeling

retrieving

and assimilation methodologies for land surface information in mountainous areas;（4） scaling effects and the validation of remote sensing products in mountainous areas; and（5） the integrated applications of remote sensing information in mountain studies. Currently

mountain remote sensing faces unprecedented developing opportunities because of the following reasons:（1） emerging novel remote sensing observation technologies

（2） in-depth development of basic theories and methodologies of mountain remote sensing

（3） driving forces from earth science big data studies

and（4） great application demands of mountain remote sensing. In this work

we reviewed the research progresses of basic theories and applications of mountain remote sensing in recent years

and analyzed the opportunities

challenges

and future prospects of mountain remote sensing in the modern era.