  Distance measurements via the dipolar interaction are fundamental to the
application of nuclear magnetic resonance (NMR) to molecular structure
determination, but they only provide information on the absolute distance $r$
and polar angle $\theta$ between spins. In this Letter, we present a protocol
to also retrieve the azimuth angle $\phi$. Our method relies on measuring the
nuclear precession phase after application of a control pulse with a calibrated
external radio-frequency coil. We experimentally demonstrate three-dimensional
positioning of individual carbon-13 nuclear spins in a diamond host crystal
relative to the central electronic spin of a single nitrogen-vacancy center.
The ability to pinpoint three-dimensional nuclear locations is central for
realizing a nanoscale NMR technique that can image the structure of single
molecules with atomic resolution.
