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Low symmetric two dimensional (2D) semiconductors are of great significance for their potential applications in polarization‐sensitive photodetection and quantum information devices. However, their real applications are limited by their photo‐detecting wavelength ranges, which are restricted by their fundamental optical bandgaps. Recently, intercalation has been demonstrated to be a powerful strategy to modulate the optical bandgaps of 2D semiconductors. Here, the authors report the self‐driven oxygen (O2) intercalation induced bandgap reduction from 1.75 to 1.19 eV in gallium telluride (GaTe) in air. This bandgap shrinkage provides the long‐wavelength detection threshold above ≈1100 nm for O2 intercalated GaTe (referred to as GaTeO2), well beyond the cut‐off wavelength at ≈708 nm for pristine GaTe. The GaTeO2 photodetectors have a high photoresponsivity, and highly anisotropic photodetection behavior to even sub‐waveband radiation. The dichroic ratio (Imax/Imin) of photocurrent is about 1.39 and 2.9 for 600 nm and 1100 nm, respectively. This findings demonstrates a broadband photodetector utilizing GaTe after breaking through its bandgap limitation by self‐driven O2 intercalation in air and further reveal its photoconductivity anisotropic nature. This provides design strategies of 2D materials‐based high‐performance broadband photodetectors for the exploration of polarized state information. [ABSTRACT FROM AUTHOR]