The fundamental theory of strong nuclear interactions between hadrons such as the proton, the neutron, the pi and K mesons and even hyperons. It is based on the fact that they are all made up of quarks, fractionally charged particles. These exist as various species called flavours and carry a specific 'charge' of the strong interaction called colour. Like quantum electrodynamics, QCD satisfies the rules of quantum mechanics and relativity and has a structure similar to so-called gauge theory.
The list of important contributors to the elaboration of this theory is vast, the foremost being Gell-Mann, Gross, Politzer,'t Hooft and Wilczek, all Nobel prize winners.