The title compound and its deuteride were synthesized by hydrogenating/deuterating SrAl 2 at 50 bar H 2 /D 2 pressure and temperatures below 200 o C. As found by in situ X-ray powder diffraction, the hydrogenation of SrAl 2 proceeds in three steps, with SrAl 2 H 2 as the first product. SrAl 2 H 2 and SrAl 2 D 2 were characterized by X-ray and neutron powder diffraction. They crystallize with a new trigonal structure in space group P3m1 (164), cell parameters: a=4.5283(1) 9, c=4.7215(2) 9 (hydride), a=4.5253(1) 9, c=4.7214(2) 9 (deuteride), Z=1. The main feature of this structure is a two-dimensional polymer Zintl anion, ~ 2 [AlH - ] 2 n , in which one H atom is covalently bonded to each Al atom. SrAl 2 H 2 is the first example of a Zintl phase hydride, i.e., the first Zintl phase in which hydrogen atoms are a part of the Zintl anion.