A chemical patent, pharmaceutical patent or drug patent is a patent for an invention in the chemical or pharmaceuticals industry. Strictly speaking, in most jurisdictions, there are essentially no differences between the legal requirements to obtain a patent for an invention in the chemical or pharmaceutical fields, in comparison to obtaining a patent in the other fields, such as in the mechanical field. A chemical patent or a pharmaceutical patent is therefore not a sui generis right, i.e. a special legal type of patent.
Chemical patent claims often use generic, Markush structures contained within them, named after the inventor Eugene Markush who won a lawsuit in the US in 1925 to allow such structures to be used in patent claims. These generic structures are used to make the patent claim as broad as possible.