  In this paper we consider discrete groups in ${\rm PGL}_d(\mathbb{R})$ acting
convex co-compactly on a properly convex domain in real projective space. For
such groups, we establish necessary and sufficient conditions for the group to
be relatively hyperbolic in terms of the geometry of the convex domain. This
answers a question of Danciger-Gu\'eritaud-Kassel and is analogous to a result
of Hruska-Kleiner for ${\rm CAT}(0)$ spaces.
