We demonstrate a rapid one-step scalable microwave heating-based method to prepare Ti3C2Tx MXenes, which shortens the synthesis time from tens of hours for state-of-the-art approaches to 15 minutes and avoids time-consuming delamination with organic compounds. Noticeably, the microwave-synthesized MXene nanosheets have a tailorable size, a stable colloidal dispersion, high electrical conductivity and superior near-infrared (NIR) photothermal conversion performance.