The carbonless structure of Hydrogen is considered as a potential fuel for future automotive propulsion system to reduce reliance on energy imports and elimination of carbon containing emissions. There are a lot of research on fuel cells, which yields very promising results, yet at other side it has several drawbacks such as cost, bulkiness and low efficiency at high loads. Here the hydrogen fuelled internal combustion engine appears on the scene. The working principle of an internal combustion engine fuelled with hydrogen is same as any spark ignition engine. This paper reviews optimistic features and current boundaries that are associated with the use of hydrogen as SI engine fuel, along with the recent advancements in hydrogen (H2) powered engine. An overview of highly favorable engine specific properties of hydrogen with regards to its combustion characteristics and challenges that must be surmounted in order to establish a “Hydrogen Economy” are described. Emphasis on Hydrogen Oxygen reaction mechanism, number of designs, and specially engine operation strategies that utilizes the full potential of hydrogen for high efficiency and low tail pipe emission is specified. This includes the significant progress required in hardware up-gradation, external & In-cylinder mixture formation strategy and safety requirement to make a conventional engine to run on hydrogen.