We report on the retrieval of Na density profiles in the mesopause region from satellite observations of the Na D-line nightglow emission near 589 nm made by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) on the Envisat spacecraft. The retrieval is based the Na D-line excitation mechanism originally proposed by Sydney Chapman in 1939. The retrieved Na profiles are compared to independent satellite measurements. The largest source of error is the remaining uncertainty of the branching ratio f for the production of Na(2P) via the reaction of NaO and O. Good agreement with independent observations is found in terms of peak altitude, peak concentration, and vertical column density, after an empirical adjustment of the branching ratio to a value of f = 0.09. This value is in good agreement with several earlier studies. The retrievals constitute the first Na profile retrievals from satellite observations of the Na D-line nightglow emission profile. They enable our understanding of the Na nightglow excitation mechanism to be tested.