Optical modulators based on two-dimensional (2D) layered materials, such as graphene, transition metal dichalcogenides (TMDs), and black phosphorus, are promising for high-performance photonic and optoelectronic applications. These materials offer unique electrical and optical properties, enabling compact, efficient, and broadband optical modulators. Recent advances include hybrid structures like 2D heterostructures, plasmonic structures, and silicon/fibre integrated devices. The review discusses the state-of-the-art of optical modulators based on these materials, highlighting their potential for applications in optical interconnects, environmental monitoring, biosensing, and medical applications. 2D materials can exhibit a wide range of physical behaviors, from wideband insulators to semimetals, and can be stacked to form 2D heterostructures without lattice mismatch issues. They are compatible with various photonic structures, such as fibre and silicon devices, enabling integration into current optical fibre networks and silicon CMOS technology. Compared to traditional bulk semiconductors, 2D materials offer mechanical flexibility, ease of fabrication, and robustness. They can perform almost all functions required for integrated photonic circuits, including photon generation, modulation, and detection. Optical modulation in 2D materials has been extensively studied, with various modulation mechanisms, such as all-optical, electro-optic, thermo-optic, magneto-optic, and acousto-optic, demonstrating competitive performance. For example, graphene-based modulators have broad operation bandwidths, covering from visible to microwave regions. TMDs and black phosphorus also show potential for specific wavelength ranges. Recent studies have demonstrated high-speed data transmission experiments at speeds up to 22 Gbit/s using 2D materials. The review also discusses the fundamentals of optical modulators, including their classification based on modulated light attributes and operation principles. Key performance metrics include modulation speed, depth, operation wavelength range, energy consumption, and insertion loss. 2D materials offer advantages in these metrics, with graphene showing high mobility and tunable bandgaps. However, challenges remain in improving modulation depth and efficiency for practical applications. 2D materials have strong light-matter interactions, enabling various nonlinear optical effects, such as second harmonic generation and nonlinear frequency conversion. These properties make them suitable for quantum light sources and integrated quantum circuits. Electro-optic modulators based on 2D materials have been demonstrated with high modulation depths and speeds, while thermo-optic and magneto-optic modulators show potential for specific applications. Acousto-optic modulators using 2D materials are also being explored for surface acoustic wave generation and detection. Overall, 2D materials offer significant advantages for optical modulators, including broad operation bandwidths, small footprints, low cost, and high flexibility. These properties enable a wide range of new photonic devices, such as tunable notch filters, spatial light modulators, smart windows, andOptical modulators based on two-dimensional (2D) layered materials, such as graphene, transition metal dichalcogenides (TMDs), and black phosphorus, are promising for high-performance photonic and optoelectronic applications. These materials offer unique electrical and optical properties, enabling compact, efficient, and broadband optical modulators. Recent advances include hybrid structures like 2D heterostructures, plasmonic structures, and silicon/fibre integrated devices. The review discusses the state-of-the-art of optical modulators based on these materials, highlighting their potential for applications in optical interconnects, environmental monitoring, biosensing, and medical applications. 2D materials can exhibit a wide range of physical behaviors, from wideband insulators to semimetals, and can be stacked to form 2D heterostructures without lattice mismatch issues. They are compatible with various photonic structures, such as fibre and silicon devices, enabling integration into current optical fibre networks and silicon CMOS technology. Compared to traditional bulk semiconductors, 2D materials offer mechanical flexibility, ease of fabrication, and robustness. They can perform almost all functions required for integrated photonic circuits, including photon generation, modulation, and detection. Optical modulation in 2D materials has been extensively studied, with various modulation mechanisms, such as all-optical, electro-optic, thermo-optic, magneto-optic, and acousto-optic, demonstrating competitive performance. For example, graphene-based modulators have broad operation bandwidths, covering from visible to microwave regions. TMDs and black phosphorus also show potential for specific wavelength ranges. Recent studies have demonstrated high-speed data transmission experiments at speeds up to 22 Gbit/s using 2D materials. The review also discusses the fundamentals of optical modulators, including their classification based on modulated light attributes and operation principles. Key performance metrics include modulation speed, depth, operation wavelength range, energy consumption, and insertion loss. 2D materials offer advantages in these metrics, with graphene showing high mobility and tunable bandgaps. However, challenges remain in improving modulation depth and efficiency for practical applications. 2D materials have strong light-matter interactions, enabling various nonlinear optical effects, such as second harmonic generation and nonlinear frequency conversion. These properties make them suitable for quantum light sources and integrated quantum circuits. Electro-optic modulators based on 2D materials have been demonstrated with high modulation depths and speeds, while thermo-optic and magneto-optic modulators show potential for specific applications. Acousto-optic modulators using 2D materials are also being explored for surface acoustic wave generation and detection. Overall, 2D materials offer significant advantages for optical modulators, including broad operation bandwidths, small footprints, low cost, and high flexibility. These properties enable a wide range of new photonic devices, such as tunable notch filters, spatial light modulators, smart windows, and