The oxide perovskites are a large family of materials with many important physical properties. Of particular interest has been the fact that this structure type provides an excellent structural framework for the existence of superconductivity. The high Tc copper oxides are the most famous examples of superconducting perovskites, but there are many others [1]. Intermetallic compounds have been the source of many superconducting materials in the past, but they have been eclipsed in recent years by the perovskite oxides. The recent discovery of superconductivity in MgB2 [2] suggests that intermetallic compounds with simple structure types are worth serious reconsideration as sources of new superconducting materials. Here we report the observation of superconductivity at 8 K in the perovskite structure intermetallic compound MgCNi3, linking what appear at first sight to be mutually exclusive classes of superconducting materials. The observation of superconductivity in MgCNi3 indicates that MgB2 will not be the only one of its kind within the chemical paradigm that it suggests for new superconducting materials.