  We present a Z_2 x Z_2 orbifold compactification of the E_8 x E_8 heterotic
string which gives rise to the exact chiral MSSM spectrum. The GUT breaking
SU(5) to SU(3)_C x SU(2)_L x U(1)_Y is realized by modding out a freely acting
symmetry. This ensures precision gauge coupling unification. Further, it allows
us to break the GUT group without switching on flux in hypercharge direction,
such that the standard model gauge bosons can remain massless when the orbifold
singularities are blown up. The model has vacuum configurations with matter
parity, a large top Yukawa coupling and other phenomenologically appealing
features.
