  Let M_0^R be the moduli space of smooth real cubic surfaces. We show that
each of its components admits a real hyperbolic structure. More precisely, one
can remove some lower-dimensional geodesic subspaces from a real hyperbolic
space H^4 and form the quotient by an arithmetic group to obtain an orbifold
isomorphic to a component of the moduli space. There are five components. For
each we describe the corresponding lattices in PO(4,1). We also derive several
new and several old results on the topology of M_0^R. Let M_s^R be the moduli
space of real cubic surfaces that are stable in the sense of geometric
invariant theory. We show that this space carries a hyperbolic structure whose
restriction to M_0^R is that just mentioned. The corresponding lattice in
PO(4,1), for which we find an explicit fundamental domain, is nonarithmetic.
