The paper presents a novel approach to all-optical ultrafast polarization switching using nonlinear plasmonic metasurfaces. The authors demonstrate a switching time of 521 femtoseconds and a modulation depth of 97% by employing second-harmonic generation (SHG) in a plasmonic metasurface with gold meta-atoms. The metasurface consists of spatially variant meta-atoms arranged in a hexagonal lattice, which exhibit strong plasmonic resonance in the near-infrared regime. By controlling the time delay between two pump beams with orthogonal linear polarizations, the polarization of the SHG waves can be switched ultrafast. The study also shows the capability of dual-channel all-optical switching, making the metasurface a promising platform for optical information processing and advanced applications such as all-optical logic gating, optical auto-correlation, and time-varying optical holography.The paper presents a novel approach to all-optical ultrafast polarization switching using nonlinear plasmonic metasurfaces. The authors demonstrate a switching time of 521 femtoseconds and a modulation depth of 97% by employing second-harmonic generation (SHG) in a plasmonic metasurface with gold meta-atoms. The metasurface consists of spatially variant meta-atoms arranged in a hexagonal lattice, which exhibit strong plasmonic resonance in the near-infrared regime. By controlling the time delay between two pump beams with orthogonal linear polarizations, the polarization of the SHG waves can be switched ultrafast. The study also shows the capability of dual-channel all-optical switching, making the metasurface a promising platform for optical information processing and advanced applications such as all-optical logic gating, optical auto-correlation, and time-varying optical holography.