We report on the discovery of pressure-induced superconductivity in the compensated semimetal pyrite PtBi2, which exhibits extreme magnetoresistance (XMR) and nontrivial band structure at ambient pressure. The appearance of superconductivity, first observed at P-C similar to 13 GPa with an onset critical temperature T-C of similar to 2.2 K, is accompanied by a pronounced enhancement of the density of electrons and holes based on Hall-effect measurements. Upon further compression, T-C remains almost unchanged up to 50.0 GPa; remarkably, the perfect electronhole compensation still holds, while the carrier mobility greatly reduces. No evident trace of structural phase transitions is detected through synchrotron x-ray diffraction over the measured pressure range of 1.5-51.2 GPa. These results highlight a multiband characteristic of the observed superconductivity, making pyrite PtBi2 unique among the compensated XMR materials where the pressure-induced superconductivity usually links to structural transitions and carrier imbalance.