This review provides a comprehensive overview of nanomaterial-based nanosensors, highlighting their applications and the classification of frequently used nanomaterials (NMs) to enhance sensitivity and selectivity. The review introduces various classifications of NMs commonly used in nanosensors, such as carbon-based, metal-based, and others, elucidating their exceptional properties, including high thermal and electrical conductivity, large surface area-to-volume ratio, and good biocompatibility. A thorough examination of literature sources was conducted to gather information on NMs-based nanosensors' characteristics, properties, and fabrication methods and their application in diverse sectors such as healthcare, environmental monitoring, industrial processes, and security. Additionally, advanced applications incorporating machine learning techniques were analyzed to enhance the sensor's performance. This review advances the understanding and development of nanosensor technologies by providing insights into fabrication techniques, characterization methods, applications, and future outlook. Key challenges such as robustness, biocompatibility, and scalable manufacturing are also discussed, offering avenues for future research and development in this field. The review discusses the history of nanotechnology, tracing its origins back to ancient times and highlighting key milestones in its development. It then provides a brief overview of nanomaterials, including their definition, properties, types, and classifications. The review categorizes NMs based on dimensionality, type, and morphology, detailing various forms such as zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) nanomaterials. It also explores the applications of different types of nanomaterials, including carbon-based, metal-based, and semiconductor-based nanomaterials, in various fields such as healthcare, environmental monitoring, and industrial processes. The review discusses the use of various nanomaterials in nanosensors, including carbon-based nanomaterials such as fullerenes, carbon nanotubes, graphene, and graphene oxide, as well as metal-based nanomaterials such as gold, silver, and platinum nanoparticles, and metal oxides. It highlights the unique properties of these nanomaterials and their potential applications in sensing technologies. The review also explores the sensing mechanisms of nanomaterials, including optical, electrochemical, and other transduction principles, and discusses the advantages and challenges of using nanomaterials in nanosensors. The review concludes by emphasizing the importance of nanomaterials in the development of advanced nanosensors and their potential for future applications in various fields.This review provides a comprehensive overview of nanomaterial-based nanosensors, highlighting their applications and the classification of frequently used nanomaterials (NMs) to enhance sensitivity and selectivity. The review introduces various classifications of NMs commonly used in nanosensors, such as carbon-based, metal-based, and others, elucidating their exceptional properties, including high thermal and electrical conductivity, large surface area-to-volume ratio, and good biocompatibility. A thorough examination of literature sources was conducted to gather information on NMs-based nanosensors' characteristics, properties, and fabrication methods and their application in diverse sectors such as healthcare, environmental monitoring, industrial processes, and security. Additionally, advanced applications incorporating machine learning techniques were analyzed to enhance the sensor's performance. This review advances the understanding and development of nanosensor technologies by providing insights into fabrication techniques, characterization methods, applications, and future outlook. Key challenges such as robustness, biocompatibility, and scalable manufacturing are also discussed, offering avenues for future research and development in this field. The review discusses the history of nanotechnology, tracing its origins back to ancient times and highlighting key milestones in its development. It then provides a brief overview of nanomaterials, including their definition, properties, types, and classifications. The review categorizes NMs based on dimensionality, type, and morphology, detailing various forms such as zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) nanomaterials. It also explores the applications of different types of nanomaterials, including carbon-based, metal-based, and semiconductor-based nanomaterials, in various fields such as healthcare, environmental monitoring, and industrial processes. The review discusses the use of various nanomaterials in nanosensors, including carbon-based nanomaterials such as fullerenes, carbon nanotubes, graphene, and graphene oxide, as well as metal-based nanomaterials such as gold, silver, and platinum nanoparticles, and metal oxides. It highlights the unique properties of these nanomaterials and their potential applications in sensing technologies. The review also explores the sensing mechanisms of nanomaterials, including optical, electrochemical, and other transduction principles, and discusses the advantages and challenges of using nanomaterials in nanosensors. The review concludes by emphasizing the importance of nanomaterials in the development of advanced nanosensors and their potential for future applications in various fields.