The new ternary polar intermetallic phase, Li2Y5In9, was obtained by high-temperature solid-state reactions of the corresponding elements inwelded Ta tubes. Its crystal structure was established by a single-crystal X-ray diffraction study. Li(2)y(5)ln(9) crystallizes in the tetragonal space group P4/nmm (No. 129) with cell parameters of a = b = 10.1242(4), c= 15.1091(10) angstrom and Z= 4. The structure of Li2Y5In9 features a two-dimensional corrugated anionic In-9 layer composed of two types of square pyramidal ln(5) units and butterfly In-4 units. There are two types of square pyramidal In-5 units: one with normal In-In bonds and another one with greatly elongated In-In separations within its In4 square. Packing of these 2D In-9 layers resulted in cavities and tunnels that are occupied by Y and Li atoms. Extended-HOckel tight-binding calculations indicate that Li(2)y(5)In(9) is metallic.