Features of the origin of $\gamma$-lines under cosmic conditions, the methodology of cosmic $\gamma$-spectroscopy, and the characteristics of $\gamma$-spectrometers are discussed. Observational data are provided on discrete ylines caused by solar flares as well as on those arising in cosmic objects outside the solar system. A possible interpretation of the detected $\gamma$-lines is discussed. In closing the article, the prospects of cosmic $\gamma$-spectroscopy are analyzed.