Micro/nanolasers (MNLs) emit coherent light on the micro/nanoscale. Research on the application of MNLs has progressed rapidly in the past two decades because of their great potential for optoelectronics with compact sizes, low cost, and low energy consumption. Wavelength‐tunable MNLs are essential for a variety of fields including optical communications, solid‐state lighting, and on‐chip wavelength‐division multiplexing. Thus far, tremendous progress is achieved toward the development of wavelength‐tunable MNLs based on bandgap tuning and cavity design. Lasing wavelength is substantially defined by material bandgap, tuned by changing the geometry of the cavity structures, and can also, to some extent, be influenced by operational environment. This review is focused on the intrinsic merits of wavelength‐tunable MNLs, and the recent progress is examined. Bandgap engineering, materials synthesis, cavity structure design, wavelength‐tuning principles, and lasing performance are explored and systematically discussed. Finally, the current research status and perspectives on possible future applications are summarized.

As an ideal miniaturized light source, wavelength-tunable nanolasers capable of emitting a wide spectrum stimulate intense interests for on-chip optoelectronics, optical communications, and spectroscopy. However, realization of such devices remains a major challenge because of extreme difficulties in achieving continuously reversibly tunable gain media and high quality (Q)-factor resonators on the nanoscale simultaneously. Here, exploiting single bandgap-graded CdSSe NWs and a Fabry–Pérot/whispering gallery mode (FP/WGM) coupling cavity, a free-standing fiber-integrated reversibly wavelength-tunable nanolaser covering a 42 nm wide spectrum at room temperature with high stability and reproducibility is demonstrated. In addition, a 1.13 nm tuning spectral resolution is realized. The substrate-free device design enables integration in optical fiber communications and information. With reversible and wide, continuous tunability of emission color and precise control per step, our work demonstrates a general approach to nanocavity coupling affording high Q-factors, enabling an ideal miniaturized module for a broad range of applications in optics and optoelectronics, with optical fiber integration.