Due to tremendous molecular recognition potential, DNA is particularly well suited macromolecule for biosensing applications. The analysis and study of gene sequences and gene polymorphisms have a significant role in quick detection of genetic mutations, which offer reliable diagnosis even before any symptoms of a disease appears. Therefore, the detection of specific DNA sequence is important in various areas as well as clinical analysis like DNA diagnostics, gene analysis, fast detection of biological warfare agents, and forensic applications and food analysis. DNA biosensors offer continuous, fast, sensitive, and selective detection and usually are based on optical or electrochemical detection. Generally, DNA biosensors rely on the immobilization of a ssDNA probe onto a surface, which can detect its complementary DNA target sequence via hybridization. In this book, we have tried to demonstrate recent advances in the application of various nanomaterials in the field of DNA biosensor. Readers of this book will be able to find out more about the properties of various nanomaterials as well as their utilization in biosensing technology.