The CRISPR-Cas9 genome-editing breakthrough revolutionises biotechnology by providing unmatched precision, efficiency, and versatility. Initially a bacterial immune response, CRISPR has evolved into a powerful tool in medicine, agriculture, and synthetic biology. By employing a programmable single-guide RNA (sgRNA) that directs the Cas9 endonuclease, this system allows for targeted genetic modifications with remarkable accuracy. In the medical field, CRISPR spearheads advances in gene therapy, cancer immunotherapy, and the treatment of genetic illnesses such as sickle cell anemia and cystic fibrosis. Its capability to edit DNA with precision has opened new avenues for personalised medicine and regenerative treatments. CRISPR is creating climate-resilient crops that boast higher yields, improved disease resistance, and enhanced nutritional value in agriculture, fundamentally changing food security. Additionally, it is influencing future livestock breeding by fostering disease resistance and lessening reliance on antibiotics. Beyond healthcare and agriculture, CRISPR is also making strides in synthetic biology, supporting microbial engineering for biofuel production, industrial enzyme development, and environmental bioremediation. Nevertheless, despite its immense potential, CRISPR encounters significant challenges such as off-target mutations, ethical dilemmas, and regulatory scrutiny. Progress in the development of high-fidelity Cas9 variants, base and prime editing, and AI-enhanced CRISPR tools, continues to refine this technology, improving its precision and safety. As CRISPR transforms genome engineering, this review delves into its mechanisms, revolutionary applications, ethical considerations, and prospective effects on biotechnology and medicine.