This Perspective reviews the properties of planar hyperbolic polaritons and the methods for tuning them in biaxial and uniaxial 2D van der Waals (vdW) crystals. Planar hyperbolic polaritons are hybrid electromagnetic modes that exhibit unique directional and broadband subdiffractional confinement. These polaritons can be found in materials such as h-BN, black phosphorus, and α-MoO₃, and their properties can be tuned through heterostructures, strain, electrostatic gates, and other techniques. The unique ray-like propagation and magic angles corresponding to topological transitions make these polaritons promising for applications in quantum and spin photonics, thermal management, sensing, subwavelength focusing, transformation optics, and polarization engineering. Hyperbolic polaritons in 2D materials can be classified into plasmon, phonon, and exciton polaritons. The hyperbolicity arises from the difference in the sign of the imaginary part of the diagonal surface conductivity components. The optical response of these materials is governed by the surface conductivity tensor, and the dispersion of polaritons is determined by the permittivity tensor. The isofrequency surfaces of these materials exhibit hyperbolic shapes, allowing for highly directional propagation. The physical origin of plasmonic hyperbolicity is due to the interplay between intraband and interband processes. In metallic systems, the collective motion of free electrons can generate strong optical absorption below the plasma frequency. The dielectric response of materials is influenced by the presence of excitons, which can lead to strong resonant absorption peaks in the optical spectra. The exciton oscillator strength is inversely related to the effective Bohr radius of the exciton, leading to prominent absorption peaks in 2D materials. The experimental observation of planar hyperbolic polaritons in vdW materials has been achieved using techniques such as s-SNOM and PiFM. These experiments have revealed the wavevector at the excitation laser frequency and the dispersion relationship for the polaritonic modes. The plasmonic hyperbolicity in WTe₂ has been observed, with the dispersion of plasmon polaritons following ω ∝ √q at low energy. The isofrequency contours of the plasmon at different energies reveal the topological transition from elliptic to hyperbolic regimes. The hyperbolicity induced by excitons is due to the contrasting spectral resonance along the crystal axes. The dielectric response of materials is influenced by the presence of excitons, which can lead to strong resonant absorption peaks in the optical spectra. The exciton oscillator strength is inversely related to the effective Bohr radius of the exciton, leading to prominent absorption peaks in 2D materials. The engineering of planar hyperbolic materials involves manipulating the symmetry and orientation of crystals, as well as using techniques such as intercalThis Perspective reviews the properties of planar hyperbolic polaritons and the methods for tuning them in biaxial and uniaxial 2D van der Waals (vdW) crystals. Planar hyperbolic polaritons are hybrid electromagnetic modes that exhibit unique directional and broadband subdiffractional confinement. These polaritons can be found in materials such as h-BN, black phosphorus, and α-MoO₃, and their properties can be tuned through heterostructures, strain, electrostatic gates, and other techniques. The unique ray-like propagation and magic angles corresponding to topological transitions make these polaritons promising for applications in quantum and spin photonics, thermal management, sensing, subwavelength focusing, transformation optics, and polarization engineering. Hyperbolic polaritons in 2D materials can be classified into plasmon, phonon, and exciton polaritons. The hyperbolicity arises from the difference in the sign of the imaginary part of the diagonal surface conductivity components. The optical response of these materials is governed by the surface conductivity tensor, and the dispersion of polaritons is determined by the permittivity tensor. The isofrequency surfaces of these materials exhibit hyperbolic shapes, allowing for highly directional propagation. The physical origin of plasmonic hyperbolicity is due to the interplay between intraband and interband processes. In metallic systems, the collective motion of free electrons can generate strong optical absorption below the plasma frequency. The dielectric response of materials is influenced by the presence of excitons, which can lead to strong resonant absorption peaks in the optical spectra. The exciton oscillator strength is inversely related to the effective Bohr radius of the exciton, leading to prominent absorption peaks in 2D materials. The experimental observation of planar hyperbolic polaritons in vdW materials has been achieved using techniques such as s-SNOM and PiFM. These experiments have revealed the wavevector at the excitation laser frequency and the dispersion relationship for the polaritonic modes. The plasmonic hyperbolicity in WTe₂ has been observed, with the dispersion of plasmon polaritons following ω ∝ √q at low energy. The isofrequency contours of the plasmon at different energies reveal the topological transition from elliptic to hyperbolic regimes. The hyperbolicity induced by excitons is due to the contrasting spectral resonance along the crystal axes. The dielectric response of materials is influenced by the presence of excitons, which can lead to strong resonant absorption peaks in the optical spectra. The exciton oscillator strength is inversely related to the effective Bohr radius of the exciton, leading to prominent absorption peaks in 2D materials. The engineering of planar hyperbolic materials involves manipulating the symmetry and orientation of crystals, as well as using techniques such as intercal