A flywheel is a mechanical device used to store and release energy during engine operation, acting as an energy reservoir. It smooths out the fluctuations in engine speed caused by the intermittent energy generation in internal combustion engines. This study focuses on the design, analysis, and optimization of a flywheel for a multi-cylinder petrol engine using CATIA for modeling and ANSYS for structural and fatigue analysis. The analysis compares the performance of flywheels made of gray cast iron and aluminum alloy to determine the optimal material for better performance and durability.