Planetary interiors strongly influence the habitability of their surfaces. The composition, dynamics, and stability of the atmosphere and surface environment are influenced by the tectonic mode, the thermal state, and magnetic field generation in the interior. Using Earth as a prototype, we review the mechanisms with which the interior is thought to influence the surface, the constraints and difficulties with thermal evolution models, the potential for strong tidal effects, the importance of planetary magnetic fields, and possible surface-interior feedbacks. We review the Earth-Venus dichotomy to illustrate how planets with similar size and bulk composition can diverge over time and emphasize the importance of considering the evolution of the planet as a whole and how divergence may be triggered by small differences. Finally, next-generation observations and theory needed to progress our understanding of the role of planetary interiors on habitability and the search for life are discussed.