In certain number of space-time dimensions, the general theory of relativity can be equivalently formulated as a theory whose classical fields are p-forms and gauge fields. Familiar examples of such "topological" gravity theories appear in Chern-Simons gravity and loop quantum gravity. In this talk we discuss higher-dimensional analogs of these theories, based on action functionals invented by Hitchin. In particular, we focus on a 7-dimensional theory whose classical solutions are metrics with G2 holonomy. We show that this theory naturally unifies all the low-dimensional topological gravities, as well as other phenomena in topological string and field theories.