In chemistry, intercalation is the reversible inclusion or insertion of a molecule (or ion) into compounds with layered structures. Examples are found in graphite intercalation compounds.

Many layered solids intercalate guest molecules. A famous example is the intercalation of potassium into graphite. Intercalation expands the van der Waals gap between sheets, which requires energy. Usually this energy is supplied by charge transfer between the guest and the host solid, i.e., redox. Two potassium graphite compounds are KC₈ and KC₂₄. Carbon fluorides (e.g., (CF)_x and (C₄F)) are prepared by reaction of fluorine with graphitic carbon. The color is greyish, white, or yellow. The bond between the carbon and fluorine atoms is covalent, thus fluorine is not intercalated. Such materials have been considered as a cathodes in various lithium batteries.