Due to their attractive electronic, optical, and thermal properties; gold nanoparticles (AuNPs) have emerged with great interest, as well as catalytic properties, in the fields of physics, chemistry, biology, medicine, material science and some interdisciplinary fields. This book examines a broad range of applications of gold nanoparticles such as: gold nanoparticles as an antigen carrier and as an adjuvant; laser synthesis of gold nanoparticles and the control over their properties; gold on carbon catalysts; gold nanoparticles as a delivery vehicle in biomedical applications; solution and solid-state methods to prepare Au nanoparticles; gold nanoparticles and their in-vitro property, the usefulness of gold nanoparticles in emerging infectious disease situations and a host of others.