The behavior of a water molecule in Na-6[AlSiO4](6) sodalite has been investigated using density functional calculations. The lowest energy position of the molecule is near the plane of the 6-ring window which does not contain a Na ion. The molecule is oriented to form hydrogen bonds with two of the framework oxygens and to interact with a Na ion in a nearby window. In this configuration the energy is 0.58 eV below the energy of the isolated water molecule plus that of anhydrous sodalite. Several tests indicate that most of the binding energy is due to the interaction of the oxygen with the Na ion. An analysis of electronic density for the lowest energy position shows that, when the molecule is put in contact with sodalite, charge is transferred from the water molecule to the spaces between the hydrogen atoms and the framework oxygens and between the water molecule oxygen and the nearest Na framework ion. Other bonding sites are above the plane of a B-ring window occupied by a Na ion and above a 4-ring window.