  We construct a class of Heterotic String vacua described by Landau--Ginzburg
theories and consider orbifolds of these models with respect to abelian
symmetries. For LG--vacua described by potentials in which at most three
scaling fields are coupled we explicitly construct the chiral ring and discuss
its diagonalization with respect to its most general abelian symmetry. For
theories with couplings between at most two fields we present results of an
explicit construction of the LG--potentials and their orbifolds. The emerging
space of (2,2)--theories shows a remarkable mirror symmetry. It also contains a
number of new three--generation models.
