Controlling the interaction of a single quantum emitter with its environment is a key challenge in quantum optics. Here, we demonstrate deterministic coupling of single nitrogen-vacancy (NV) centers to high-quality photonic crystal cavities. We preselect single NV centers and position their 50-nm-sized host nanocrystals into the mode maximum of photonic crystal S1 cavities with few-nanometer accuracy. The coupling results in a strong enhancement of NV center emission at the cavity wavelength.