Tourmaline is a boron-bearing cyclosilicate mineral with complex chemical compositions. It can remain stable in a wide range of p-t conditions (t=150~900℃, p=6 MPa~6 GPa), making it an ideal tracer mineral for understanding geological process in different tectonic environments. We provide a comprehensive summary of the mineralogical characteristics and geochemical compositions of tourmaline, with a particular focus on the main factors controlling its boron isotopic compositions, including the boron source, equilibrium and/or Rayleigh fractionation, and the evolution of ore deposit. We further summarize and review the applications of tourmaline in key areas, including its major and trace elements, stable isotopes (H-O, Si, B), and radiogenic isotopes (Rb-Sr, Sm-Nd) for tracing the sources and evolution of geological fluids, as well as its role in investigating the metallogenic processes of various deposit types (e.g., IOCG and orogenic gold deposits). Finally, this study highlights several promising directions for future research on tourmaline. In particular, further investigations are expected to achieve breakthroughs in crystal-chemical structure determination, in-situ micro-scale isotopic analyses (e.g., Li, Mg), the construction of p-t-T trajectories to trace fluid evolution, and the reconstruction of paleo-seawater boron isotope signatures. Comprehensive studies integrating tourmaline mineral chemistry, isotope geochemistry, and geochronological approaches will not only advance our understanding of fluid formation and evolutionary mechanisms, but may also provide crucial clues for deciphering the environmental evolution of early Earth.