The paper presents a first-principles calculation of quasiparticle energies and band gaps for graphene nanoribbons (GNRs) using the GW approximation within the many-electron Green's function approach. The quasi-one-dimensional nature of GNRs, combined with enhanced electron-electron interactions due to screening and confinement, significantly affects the quasiparticle band gap. The calculated quasiparticle band gaps for both armchair and zigzag GNRs show significant self-energy corrections ranging from 0.5 to 3.0 eV for ribbons with widths from 2.4 to 0.4 nm. These results suggest that GNRs may be viable for electronic device components in ambient conditions. The study also highlights the importance of considering spin polarization and the impact of edge states on the band structure, particularly in zigzag GNRs. Experimental data for wider GNRs (15-90 nm) align with the calculated trends, but direct comparison is challenging due to differences in passivation methods and sample preparation. Overall, the calculated quasiparticle band gaps fall within an attractive range (1-3 eV) for 2-1 nm GNRs, indicating potential applications in nanoelectronics.The paper presents a first-principles calculation of quasiparticle energies and band gaps for graphene nanoribbons (GNRs) using the GW approximation within the many-electron Green's function approach. The quasi-one-dimensional nature of GNRs, combined with enhanced electron-electron interactions due to screening and confinement, significantly affects the quasiparticle band gap. The calculated quasiparticle band gaps for both armchair and zigzag GNRs show significant self-energy corrections ranging from 0.5 to 3.0 eV for ribbons with widths from 2.4 to 0.4 nm. These results suggest that GNRs may be viable for electronic device components in ambient conditions. The study also highlights the importance of considering spin polarization and the impact of edge states on the band structure, particularly in zigzag GNRs. Experimental data for wider GNRs (15-90 nm) align with the calculated trends, but direct comparison is challenging due to differences in passivation methods and sample preparation. Overall, the calculated quasiparticle band gaps fall within an attractive range (1-3 eV) for 2-1 nm GNRs, indicating potential applications in nanoelectronics.