The production of textile materials has undergone dramatic changes in the last century. Man-made cellulose fibres have played an important role for more than 70 years. Today, the man-made cellulose fibre industry is the worldwide second largest biorefinery (next to the paper industry). In the last few years, the interest in man-made cellulose fibres has grown as a consequence of increased environmental awareness and the depletion of fossil fuels. However, an environmental assessment of modern man-made cellulose fibres has not been conducted so far. The purpose of this study is to assess the environmental impact of man-made cellulose fibres. Five staple fibre products, i.e., 1) Lenzing Viscose Asia, 2) Lenzing Viscose Austria, 3) Lenzing Modal, 4) Tencel Austria, and 5) Tencel Austria 2012, are analysed by means of Life cycle assessment (LCA). The system boundary is cradle to factory gate. We compare the results with conventional cotton, novel bio-based fibres (PLA fibres), and fossil fuel-based fibres (PET and PP). The inventory data for the production of man-made cellulose fibres were provided by Lenzing AG. The inventory data for cotton, PET, PP, and PLA were obtained from literature sources. The environmental indicators analysed include resources and the impact categories covered by CML 2000 baseline method. The indicators for resources include non-renewable energy use (NREU), renewable energy use (REU), cumulative energy demand (CED), water use, and land use. The environmental impact indicators covered by the CML method are global warming potential (GWP) 100a, abiotic depletion, ozone layer depletion, human toxicity, fresh water aquatic ecotoxicity, terrestrial ecotoxicity, photochemical oxidation, acidification, and eutrophication. In addition, the system boundary of cradle to factory gate plus end-of-life waste management was analysed for NREU and GWP. Furthermore, sensitivity analyses have been carried out to understand the influence of various assumptions and allocation methods. The LCA results show that Lenzing Viscose Austria and Lenzing Modal offer environmental benefits in all categories (except for land use and water use) compared to Lenzing Viscose Asia. Tencel Austria 2012, Lenzing Viscose Austria, Lenzing Modal, and Tencel Austria are the most favourable choices from an environmental point of view among all the fibres studied. These four man-made cellulose fibres offer important benefits for reducing NREU, GWP, toxicity impacts, water use, and land use. Lenzing Viscose Asia has higher impacts than the other man-made cellulose fibres with regard to NREU, GWP, abiotic depletion, photochemical oxidation, and acidification. Cotton is identified as the least preferred choice due to its high ecotoxicity impacts, eutrophication, water use, land use, and relatively low land use efficiencies.