Cosmetic composition comprising anionic surfactants, amphoteric surfactants, cationic polymers and liquid fatty substances chosen from fatty alcohols and fatty esters, and cosmetic treatment process The present invention relates to a cosmetic composition, especially a hair composition, comprising: —one or more anionic surfactants, —one or more amphoteric surfactants, —one or more cationic polymers with a high cationic charge density, —one or more liquid fatty substances chosen from non-oxyalkylenated fatty alcohols and monocarboxylic fatty acid esters, and also mixtures thereof. The invention also relates to a cosmetic process for treating, and more particularly for washing and conditioning, keratin materials, especially the hair, using the present composition.