Solution-processed semiconductor lasers have achieved much success across the nanomaterial research community, including in relation to organic semiconductors1,2, perovskites3,4 and colloidal semiconductor nanocrystals5,6. The ease of integration with other photonic components and the potential for upscaling using emerging large-area fabrication technologies (such as roll-to-roll7) make these lasers attractive as low-cost photonic light sources that can find use in a variety of applications, including integrated photonic circuitry8,9, telecommunications10,11, chemo-/bio-sensing12,13, security14 and lab-on-chip experiments15. However, for fibre-optic or free-space optical communications and eye-safe LIDAR applications, room-temperature solution-processed lasers have remained elusive. Here, we report a solution-processed laser comprising PbS colloidal quantum dots integrated on a distributed feedback cavity, with tunable lasing wavelength from 1.55 μm to 1.65 μm. These lasers operate at room temperature and exhibit linewidths as low as ~0.9 meV.