Clean code is software written to maximize readability, maintainability, and comprehension by human developers, not just machines. Originating from Robert C. Martin's influential work, clean code principles have become the foundation of professional software craftsmanship across all programming paradigms. These practices reduce technical debt, accelerate team velocity, and prevent the gradual decay that transforms codebases into unmaintainable "legacy" systems. The key insight: code is read far more often than it is written—optimizing for the reader, including your future self, is the highest form of professional responsibility.