The field of nanotechnology has revolutionized the landscape of biomedical science by introducing materials that operate at the molecular and cellular level. Among these, biocompatible nanomaterials have emerged as a pivotal class of substances, offering exceptional promise for diagnostic, therapeutic, and regenerative applications. This chapter provides a brief yet comprehensive overview of biocompatible nanomaterials, focusing on their key properties, types, synthesis, and applications in biomedical science. It traces the historical development of the field and highlights essential characteristics such as biocompatibility, biodegradability, and surface functionalization. Various classes of nanomaterials—metals, polymers, lipids, carbon-based, and natural biomaterials—are discussed along with their synthesis methods, including green approaches. Characterization techniques and safety evaluations, including in vitro and in vivo assessments, are outlined. The chapter also addresses recent advancements, regulatory aspects, and future perspectives in the safe and effective use of biocompatible nanomaterials in healthcare.