We describe the first demonstration and characterization of an optically integrated InP-Si3N4 hybrid laser. The laser is formed by integration of an InP-based reflective semiconductor optical amplifier with a InP-Si3N4 based feedback waveguide circuit. The circuit comprises a frequency selective and tunable Vernier mirror composed of two microring resonators with slightly different radii. A wide tuning range of more than 43 nm is achieved via the thermo-optic effect. The typical side mode suppression ratio is 35 dB. The narrowest linewidth achieved is about 90 kHz, and the relative intensity noise is less than -135 dBc/Hz.