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The H3 Survey (for Hectochelle in the Halo at High Resolution) is a spectroscopic survey of about 300,000 select stars in the Milky Way halo. The goal is radial velocity (RV) measurements as well as stellar parameter determination, ultimately to complete the acquisition of the observed stars' six dimensions within phase space (i.e., covering both position and momentum). Gaia provides position and proper motion data, but its spectroscopic observations do not provide useful data to the same magnitude as does its astrometry. H3 observations are being carried out with MMT's Hectochelle multi-object spectrograph, which has 300 fiber feeds.