The Ga 2 O 3 solar-blind photodetectors (SBPDs) face the tradeoff between power consumption (<inline-formula> <tex-math notation="LaTeX">P_{\text {C}} </tex-math></inline-formula>) and photoresponse performance. Here, an ultrasensitive two-terminal photodetector based on <inline-formula> <tex-math notation="LaTeX">\boldsymbol {\beta } </tex-math></inline-formula>-Ga 2 O 3 microflake with extremely-low working voltage and <inline-formula> <tex-math notation="LaTeX">{P}_{\text {C}} </tex-math></inline-formula> was achieved. At a working voltage of 2 V and <inline-formula> <tex-math notation="LaTeX">{P}_{\text {C}} </tex-math></inline-formula> of 10 fW, the Ga 2 O 3 SBPD exhibits superexcellent photodetection performance, including a responsivity (<inline-formula> <tex-math notation="LaTeX">{R} </tex-math></inline-formula>) of <inline-formula> <tex-math notation="LaTeX">{2.3}\,\,\times \,\,{10}^{{5}}\text{A} </tex-math></inline-formula>/W, a detectivity (<inline-formula> <tex-math notation="LaTeX">{D}^{ \boldsymbol {\ast }} </tex-math></inline-formula>) of <inline-formula> <tex-math notation="LaTeX">{3.5}\,\,\times \,\,{10}^{{18}} </tex-math></inline-formula> Jones, a photo-to-dark-current ratio ( PDCR ) of <inline-formula> <tex-math notation="LaTeX">{3.2}\,\,\times \,\,{10}^{{8}} </tex-math></inline-formula>, and an ultra-low dark current (<inline-formula> <tex-math notation="LaTeX">{I}_{\text {dark}} </tex-math></inline-formula>) of 5 fA. Strikingly, the device keeps satisfactory performance at ultralow working voltage of 0.01 V, including a <inline-formula> <tex-math notation="LaTeX">{P}_{\text {C}} </tex-math></inline-formula> of 0.05 fW, a <inline-formula> <tex-math notation="LaTeX">{R} </tex-math></inline-formula> of <inline-formula> <tex-math notation="LaTeX">{2.4}\,\,\times \,\,{10}^{{3}} </tex-math></inline-formula> A/W, a <inline-formula> <tex-math notation="LaTeX">{D}^{ \boldsymbol {\ast }} </tex-math></inline-formula> of <inline-formula> <tex-math notation="LaTeX">{5.6}\,\,\times \,\,{10}^{{16}} </tex-math></inline-formula> Jones, and a PDCR of <inline-formula> <tex-math notation="LaTeX">{3.4}\,\,\times \,\,{10}^{{6}} </tex-math></inline-formula>. The superior solar-blind sensitivity makes it the most excellent Ga 2 O 3 detector towards high-performance and low-<inline-formula> <tex-math notation="LaTeX">P_{\text {C}} </tex-math></inline-formula> SBPD applications.