This study investigates the highly anisotropic and robust excitons in monolayer black phosphorus using polarization-resolved photoluminescence (PL) measurements at room temperature. The researchers found that the emitted light from monolayer black phosphorus is linearly polarized along the direction of the light effective mass, centered around 1.3 eV, indicating the presence of highly anisotropic bright excitons. Photoluminescence excitation spectroscopy revealed a quasiparticle bandgap of 2.2 eV, leading to an estimated exciton binding energy of approximately 0.9 eV, consistent with theoretical predictions based on first-principles calculations. The observation of these highly anisotropic, bright excitons with large binding energies opens new avenues for exploring many-electron effects in this unique 2D material and suggests potential applications in optoelectronic devices, such as on-chip infrared light sources. The study also provides direct evidence of highly anisotropic carrier mobility in monolayer black phosphorus, which could be utilized in advanced electronic devices and circuits.This study investigates the highly anisotropic and robust excitons in monolayer black phosphorus using polarization-resolved photoluminescence (PL) measurements at room temperature. The researchers found that the emitted light from monolayer black phosphorus is linearly polarized along the direction of the light effective mass, centered around 1.3 eV, indicating the presence of highly anisotropic bright excitons. Photoluminescence excitation spectroscopy revealed a quasiparticle bandgap of 2.2 eV, leading to an estimated exciton binding energy of approximately 0.9 eV, consistent with theoretical predictions based on first-principles calculations. The observation of these highly anisotropic, bright excitons with large binding energies opens new avenues for exploring many-electron effects in this unique 2D material and suggests potential applications in optoelectronic devices, such as on-chip infrared light sources. The study also provides direct evidence of highly anisotropic carrier mobility in monolayer black phosphorus, which could be utilized in advanced electronic devices and circuits.