Novel ternary Laves phase compounds were explored, and Mg2Ir3Si was synthesized via a solid-state reaction. X-ray diffraction studies revealed that Mg2Ir3Si crystallizes in a Mg2Cu3Si-type structure ( P 63/ mmc , D 6 h 4, No. 194), which corresponds to a fully ordered variant of hexagonal Laves phase MgZn2. The structure is composed of a hexagonal diamond network of Mg atoms, a breathing Kagome network of Ir atoms, and a triangular network of Si atoms. Electrical resistivity, magnetization, and specific heat measurements of Mg2Ir3Si revealed that it exhibits superconductivity with a transition temperature of 7 K. This compound is compared to another Laves... phase compound, Li2IrSi3, in which the positions of Ir and Si are interchanged; Li2IrSi3 has a superconducting transition temperature of 3.8 K. The results obtained demonstrate that both Ir and Si Kagome networks can occur in fully ordered Laves phase compounds, i.e., in Mg2Ir3Si and Li2IrSi3, and the former is preferable for superconductivity.