This study aims to improve the efficiency of the automotive parts manufacturing process, with a focus on the stamping operation. Lean Manufacturing principles, specifically ECRS (Eliminate, Combine, Rearrange, Simplify) and Kaizen, were applied to identify and reduce production waste, particularly defect-related waste. An analysis of the existing system revealed a high defect rate in the stamping process as the primary source of inefficiency. Lean-based improvements were implemented to address root causes and minimize non-value-added activities. As a result, the defect rate was reduced from 0.69% to 0.37%, representing an improvement of approximately 46%. A 2-proportion Z-test confirmed that the reduction in defects was statistically significant (p-value < 0.001). The findings demonstrate that integrating Lean tools with process-level improvements can effectively enhance process performance and production reliability. This study provides a practical case of Lean implementation with measurable quality improvement in automotive manufacturing.