This chapter traces the intellectual heritage of Six Sigma back to its forerunners, Total Quality Management and the Toyota Production System, revealing how these earlier movements laid the groundwork for its development. Total Quality Management transformed organizational thinking by insisting that quality must permeate every function rather than be a final inspection step, fostering leadership engagement, employee involvement, and an enduring focus on customer satisfaction. At the same time, Toyota’s production philosophy introduced just-in-time workflows, automation with a human touch, and the practice of kaizen—continuous, incremental improvement—while championing waste elimination and frontline problem-solving. Six Sigma emerged as a synthesis of these ideas, preserving TQM’s customer-centric culture and TPS’s operational discipline but adding an unprecedented layer of statistical rigor. By embedding quantitative tools into each phase of its project methodology, Six Sigma replaced anecdote and intuition with data-driven decision making and measurable performance targets. The structured DMAIC framework—Define, Measure, Analyze, Improve, Control—ensures that process enhancements are both deeply researched and reliably sustained. Over time, Six Sigma has further evolved into Lean Six Sigma, marrying waste-reduction techniques with variation control to deliver faster, more precise improvements. Understanding these roots is vital for adapting Six Sigma to new contexts, as its power arises from blending cultural commitment to quality with disciplined analytical practices.