  We demonstrate that a phenomenologically viable four-dimensional grand
unified theory with no proton decay can be constructed. This is done in the
framework of the minimal non-supersymmetric SU(5) GUT by introducing new
representations and separating the physical quark and lepton fields into
different multiplets. In such a theory all beyond Standard Model particles are
naturally heavy, but one can tune the parameters of the model such that gauge
coupling unification is achieved and some of the new particles are at the TeV
scale and accessible at the LHC.
