  One of the fundamental questions about the high temperature cuprate
superconductors is the size of the Fermi surface (FS) underlying the
superconducting state. By analyzing the single particle spectral function for
the Fermi Hubbard model as a function of repulsion $U$ and chemical potential
$\mu$, we find that the Fermi surface in the normal state reconstructs from a
large Fermi surface matching the Luttinger volume as expected in a Fermi
liquid, to a Fermi surface that encloses fewer electrons that we dub the
"Luttinger Breaking" (LB) phase, as the Mott insulator is approached. This
transition into a non-Fermi liquid phase that violates the Luttinger count, is
a continuous phase transition at a critical density in the absence of any other
broken symmetry. We obtain the Fermi surface contour from the spectral weight
$A_{\vec{k}}(\omega=0)$ and from an analysis of the poles and zeros of the
retarded Green's function $G_{\vec{k}}^{ret}(E=0)$, calculated using
determinantal quantum Monte Carlo and analytic continuation methods.We discuss
our numerical results in connection with experiments on Hall measurements,
scanning tunneling spectroscopy and angle resolved photoemission spectroscopy.
