Although graphene oxide (GO) lamellar membranes have emerged as attractive candidate of membrane technology for advanced molecular separation in water treatment, their organic solvent nanofiltration performance is significantly limited by almost impermeability of organic solvents through GO membranes. Here, we present a two-dimensional (2D) GO/MXene (GM) composite lamellar membrane fabricated by facile vacuum filtration method for ultrafast water and organic solvent permeation and molecular separation. Benefiting from the similar 2D structure and hydrophilic property of MXene nanosheets with GO, the resultant GM membranes possessed typical lamellar structure with increased interlayer spacing compared to GO membranes and excellent surface wettability to water and organic solvents. The effects of MXene content on the structure, solvent permeation and molecular separation performance of GM membranes were systematically investigated. The GM membranes exhibited ultrahigh flux for pure solvents (21.02, 48.32, 25.03, 10.76, 6.18 L/m(2)h for water, acetone, methanol, ethanol and IPA) and outstanding dyes molecular separation performance (over 90%) in both aqueous and organic solutions. The relationship between solvent viscosity, dyes solubility and separation performance of GM membranes was further demonstrated. Moreover, long-term operation studies also revealed the stability of GM membranes with the different solvents and indicated their potential for practical applications.