Cantilever-based freestanding microring lasers were demonstrated based on InGaP/InGaAlP quantum wells emitting in the red region. The rotational symmetry of the microring cavity is broken by introducing the connected cantilevers, which induce degenerated mode splitting and single mode lasing emission. The connected cantilevers can not only provide mechanical support for freestanding microring lasers but also function as waveguides for efficient light extraction. In addition, the application of cantilever-based microring lasers had been studied for a refractive index sensor with a measured sensitivity of ∼7.3 nm per refractive index unit and flexible local strain gauges with the measured gauge factor of ∼6.33 nm per stretching unit.