This study reports the experimental observation and theoretical modeling of quantum spin liquid (QSL) signatures in monolayer 1T-NbSe₂, a two-dimensional material that exhibits both charge-density-wave (CDW) and correlated insulating behaviors. Using scanning tunneling microscopy and spectroscopy (STM/STS), the researchers confirmed the presence of spin fluctuations in monolayer 1T-NbSe₂ by observing Kondo resonance when interacting with metallic monolayer 1H-NbSe₂. STM/STS imaging at the Hubbard band energy revealed long-wavelength charge modulation, consistent with spinon modulation expected in QSLs. By depositing manganese-phthalocyanine (MnPc) molecules with \( S = 3/2 \) spin onto monolayer 1T-NbSe₂, new STS resonance peaks emerged at the Hubbard band edges, indicating the spinon Kondo effect induced by a magnetic impurity in a QSL. These findings collectively suggest that monolayer 1T-NbSe₂ is a promising QSL material with a spinon Fermi surface (SFS). The study provides conclusive evidence for QSL behavior in monolayer 1T-NbSe₂, supporting its potential as a new platform for investigating QSL physics in 2D quantum materials.This study reports the experimental observation and theoretical modeling of quantum spin liquid (QSL) signatures in monolayer 1T-NbSe₂, a two-dimensional material that exhibits both charge-density-wave (CDW) and correlated insulating behaviors. Using scanning tunneling microscopy and spectroscopy (STM/STS), the researchers confirmed the presence of spin fluctuations in monolayer 1T-NbSe₂ by observing Kondo resonance when interacting with metallic monolayer 1H-NbSe₂. STM/STS imaging at the Hubbard band energy revealed long-wavelength charge modulation, consistent with spinon modulation expected in QSLs. By depositing manganese-phthalocyanine (MnPc) molecules with \( S = 3/2 \) spin onto monolayer 1T-NbSe₂, new STS resonance peaks emerged at the Hubbard band edges, indicating the spinon Kondo effect induced by a magnetic impurity in a QSL. These findings collectively suggest that monolayer 1T-NbSe₂ is a promising QSL material with a spinon Fermi surface (SFS). The study provides conclusive evidence for QSL behavior in monolayer 1T-NbSe₂, supporting its potential as a new platform for investigating QSL physics in 2D quantum materials.