This overview focuses on published data related to worldwide research on fish authentication/adulteration. In the case of food analysis and control in particular, many threats are being eliminated since appropriate analytical and chemometric tools are preferable for achieving security. This chapter presents a systematic literature review of the identification of geographical origin on the basis of appropriate state-of-the-art analytical methods/techniques. Traceability of the geographic provenance of fish flesh to preserve its quality is important. Special attention is given to presenting data covering fish authenticity in terms of interspecies and interregional differentiation related to various parameters, i.e. identification of wild and farmed fish; age, sex and seasonal variations; differentiation between farming systems; the influence of pollution, etc. Combined analytical and chemometric techniques appear to be useful tools for verifying authenticity. This aspect has become an important issue for authorities involved in the protection of consumers against fraudulent practices.