Solvent extraction is a common technique utilized for both industrial applications and in the laboratory. The technique is successfully applied as a sample preparation procedure for chromatography. It can be used for separation purposes by using selective extractions, or for concentration purposes. The extraction can be applied to liquids (liquid–liquid extraction, LLE), to solid samples (liquid–solid extraction, LSE), to gas samples, and to semisolid samples. The chapter starts with a description of parameters describing the liquid–liquid equilibrium, and with a discussion on various parameters used for the characterization of solvents. It continues with the presentation of common LLE procedures, and then with that of special LLEs such as single drop microextraction, membrane-assisted solvent extraction (MASE), microporous membrane liquid–liquid extraction, hollow fiber liquid-phase microextraction, liquid–liquid–liquid microextraction, dispersive liquid–liquid microextraction, salting-out-assisted LLE, cloud point extraction, etc. Conventional LSE, as well as accelerated solvent extraction, microwave-assisted solvent extraction (MWASE), and supercritical solvent extraction are also presented including some theoretical aspects and practice of these procedures.