Two-dimensional (2D) materials have significantly transformed the class of next-generation photodetectors by facilitating tunable, high-performance, and multifunctional photodetectors. Their unique structural and electronic properties, quantum confinement effects, and anisotropic characteristics make them ideal candidates for applications across visible, infrared (IR), ultraviolet (UV), and broadband spectral domains. This chapter provides a comprehensive overview of 2D materials, including graphene, TMDs, BP, MXenes, and emerging materials like borophene and antimonide, emphasizing the tunability and sensitivity of their optical and electronic properties. Additionally, it discusses the recent advancements in device architectures, including heterostructures, plasmonically enhanced devices, and hybrid systems integrating 2D materials with organic semiconductors, perovskites, and quantum dots. The chapter further discusses the key challenges related to device optimization, stability, and large-scale integration while highlighting future prospects, including the role of machine learning and AI in predictive modeling for photodetector performance enhancement. Finally, a detailed analysis of applications across spectral domains underscores the impact of 2D materials in next-generation imaging, sensing, and optoelectronic technologies.