Gene therapy, an approach for treatment or prevention of diseases associated with defective gene expression, involves the insertion of a therapeutic gene into cells, followed by expression and production of the required proteins. This approach enables replacement of damaged genes or expression inhibition of undesired genes. This book covers recent developments related to various non-viral gene delivery systems with a basis in nanotechnology. The book is organized based on the nature of the nanomaterials: inorganic; graphene (carbon nanotubes); proteins and peptides; lipids; and other polymers. It introduces the most important cationic polymers used for gene delivery.