We present the experimental demonstration of a novel class of hybrid III-V-on-silicon microlasers. We show that by coupling a silicon cavity to a III-V waveguide, the interaction between the propagating mode in the III-V waveguide and the cavity mode in the silicon resonator results in high, narrowband reflection back into the III-V waveguide, forming a so-called resonant mirror. By combining two such mirrors and providing optical gain in the III-V wire between these two mirrors, laser operation can be realized. This optically pumped device measures 55 by 2 μm, requires microwatt-level threshold pump power, and shows single-mode laser emission with a side-mode suppression ratio of up to 39 dB.