ZnO nanoribbons with pseudo‐rectangular cross‐sections (see Figure) are demonstarted to be excellent microcavities with a high quality factor (∼ 3000). The lasing threshold is shown to be inversely proportional to the length of the ribbon for pumping intensities lower than the saturation region. Analysis of the emission spectra points to the possibility of the existence of both pure axial modes and “bow‐tie” cavity modes.