There is a well-known and satisfactory theory for the classes of Gorenstein projective, Gorenstein injective, and Gorenstein flat modules. In this paper, the authors establish a relative version of this theory. More precisely, for suitable classes \(\mathcal X\) and \(\mathcal Y\) of modules they consider the so-called \(\mathcal X\)-Gorenstein projective, \(\mathcal Y\)-Gorenstein injective, and \(\mathcal Y\)-Gorenstein flat modules, which are subclasses of the (ordinary) Gorenstein projective, Gorenstein injective, and Gorenstein flat modules, respectively. The results and the proofs found in the paper are as one would expect.