Abstract: This invention relates to internal combustion engines and particularly to igniting the fuel/air mixture of the engine. In more detail a catalytic engine comprises one or more cylinders, each cylinder having an associated piston and an entry port disposed at the top or in the region of the top of the cylinder and leading into a passage in communication with a precombustion chamber, means for injecting fuel into the combustion chamber, and a catalytic unit disposed across the entry port or across the said passage for catalytically igniting an injected fuel/air mixture, the catalytic unit including a thermally stable and oxidation resistant member having a multiplicity of flow paths or channels, the surfaces of which possess catalytic activity.