  For purposes of regularization as well as numerical simulation, the
discretization of Lorentz invariant continuum field theories on a space-time
lattice is often convenient. In general, this discretization destroys the
rotational or Lorentz-frame independence of the theory, which is only recovered
in the continuum limit. The Baxter 8-vertex model may be interpreted as a
particular discretization of a self-interacting massive Dirac fermion theory in
two dimensions (the massive Thirring model). Here it is shown that, in the
8-vertex/massive Thirring model, the Lorentz frame independence of the theory
remains undisturbed on the lattice. The only effect of the discretization is to
compactify the manifold of Lorentz frames. The relationship between this
lattice Lorentz symmetry and the Yang-Baxter relations is discussed.
