This thesis investigates the structural behavior and optimization potential of an automotive piston–connecting rod assembly using finite element analysis and topology optimization. After establishing the design requirements and modeling a baseline piston system, a detailed FEA was conducted under peak combustion loading to identify stress distribution, deformation, and stiffness characteristics. The results showed that the steel connecting rod and cap had significant weight-reduction potential due to their high safety margins. A density-based topology optimization was then applied with manufacturability constraints, leading to a redesigned component that preserved stiffness while removing low-stress material. The optimized design achieved a substantial 26.6% mass reduction without compromising structural integrity. Overall, the thesis demonstrates a practical and effective workflow for lightweighting reciprocating engine components to improve efficiency and performance.