2D materials, such as graphene, transition metal dichalcogenides, black phosphorus, and tellurium, have been demonstrated to be promising building blocks for the fabrication of next-generation high-performance infrared (IR) photodetectors with diverse device architectures and impressive device performance. Integrating IR photodetectors with nanophotonic structures, such as surface plasmon structures, optical waveguides, and optical cavities, has proven to be a promising strategy to maximize the light absorption of 2D absorbers, thus enhancing the detector performance. In this review, the state-of-the-art progress of IR photodetectors is comprehensively summarized based on 2D materials and nanophotonic structures. First, the advantages of using 2D materials for IR photodetectors are discussed. Following that, 2D material-based IR detectors are classified based on their composition, and their detection mechanisms, key figures-of-merit, and the principle of absorption enhancement are discussed using nanophotonic approaches. Then, recent advances in 2D material-based IR photodetectors are reviewed, categorized by device architecture, i.e., photoconductors, van der Waals heterojunctions, and hybrid systems consisting of 2D materials and nanophotonic structures. The review is concluded by providing perspectives on the challenges and future directions of this field.