This chapter describes the phenomenon of Raman scattering from the point of view of classical electrodynamics and quantum mechanics. Raman scattering is a type of inelastic scattering of light by molecules that changes the energy of a photon by the energy equal to a vibrational transition of that molecule. The symmetry of vibrational modes and the activity of vibrational modes in Raman spectra is discussed via group theory for molecules and minerals. The chapter describes how the information gleaned from Raman spectra can be used to identify structural information about a given sample and how this information can be useful to Earth and planetary scientists. The principal components of laboratory and remote Raman instrumentation are defined, including excitation sources, spectrographs, and detectors, and the ways in which recent advances in technology have facilitated the application of Raman spectroscopy for Earth and planetary science are discussed. Some technological advances include the development of reliable continuous wave (CW) and pulsed lasers at a variety of wavelengths, the advancement of multichannel detectors such as two-dimensional charge-coupled devices and photodiode arrays, and the coupling of optical accessories such as microscopes and telescopes. The applications of these advanced Raman systems in the fields of Earth and planetary science are highlighted.