Graphene has attracted much attention for the realization of high-speed photodetection for silicon photonics over a wide wavelength range. However, the reported fast graphene photodetectors mainly operate in the 1.55μm wavelength band. In this work, we propose and realize high-performance waveguide photodetectors based on bolometric/photoconductive effects by introducing an ultrathin wide silicon?graphene hybrid plasmonic waveguide, which enables efficient light absorption in graphene at 1.55μm and beyond. When operating at 2μm, the present photodetector has a responsivity of～70 mA/W and a setup-limited 3 dB bandwidth of>20 GHz. When operating at 1.55μm, the present photodetector also works very well with a broad 3 dB bandwidth of>40 GHz (setup-limited) and a high responsivity of～0.4 A/W even with a low bias voltage of?0.3 V. This work paves the way for achieving high-responsivity and high-speed silicon–graphene waveguide photodetection in the near/mid-infrared ranges, which has applications in optical communications, nonlinear photonics, and on-chip sensing.