Synthetic biology is an interdisciplinary field that integrates principles from biology, engineering, and computer science to design and construct new biological systems or re-engineer existing ones. This comprehensive review explores the theoretical foundations, techniques, methodologies, applications, and ethical considerations of synthetic biology. Key principles such as modularity, standardization, and abstraction facilitate the systematic design and construction of synthetic biological systems. Advanced techniques like gene synthesis, CRISPR-Cas9 genome editing, pathway engineering, and synthetic genomes are driving the field forward. Applications in healthcare, industrial biotechnology, environmental management, and agriculture highlight the transformative potential of synthetic biology. However, the field faces significant technical, regulatory, and ethical challenges, including the complexity of biological systems, biosafety concerns, and public perception. Emerging trends such as advanced gene editing technologies, artificial intelligence, biofoundries, and collaborative global initiatives are poised to address these challenges and propel the field into new frontiers. This review underscores the importance of developing robust regulatory frameworks, engaging in ethical deliberations, and fostering public engagement to ensure the responsible and beneficial development of synthetic biology. By addressing these challenges, synthetic biology can unlock innovative solutions to global issues, paving the way for a sustainable and prosperous future.