X-ray reflectivity and vibrational sum frequency spectroscopy are used to probe the structure of the ethylammonium nitrate (EAN)-air interface. X-ray reflectivity reveals that the EAN-air interface is structured and consists of alternating nonpolar and charged layers that extend 31 Å into the bulk. Vibrational sum frequency spectroscopy reveals interfacial cations have their ethyl moieties oriented toward air, with the CH3 C3 xis positioned ∼36.5° from interface normal. This structure is invariant between. 1.5 and 51°C. On account of its molecular symmetry, the orientation of the nitrate anion cannot be determined with certainty.