We define a Gauss map of
an orientable hypersurface in a homogeneous manifold with an invariant Riemannian
metric. Our main objective is to extend to this setting some results on the Gauss
map of a constant mean curvature hypersurface of an Euclidean space, namely
the Ruh–Vilm theorem relating the harmonicity of the Gauss map and the
constancy of the mean curvature, and the Hoffman–Osserman–Schoen theorem
characterizing the plane and the circular cylinder as the only complete constant mean
curvature surfaces whose Gauss image is contained in a closed hemisphere of the
sphere.