AbstractLignocellulosic biomass (LB) is potentially a relatively inexpensive and abundant feedstock for ethanol production. One of the most challenging steps during the lignocellulosic ethanol production is to convert the carbohydrates in LB to the fermentable reducing sugars (FRS) in an economically viable and environmentally friendly way. The acid-catalyzed hydrolysis of LB in ionic liquids (ILs) has provided a promising technical tool to improve upon the traditional FRS production process. Compared to the conventional FRS production process from LB via the acid or enzymatic hydrolysis method, it has many advantages, such as a simplified process, mild reaction conditions, low acid consumption, and low equipment investment. However, there are still some technical challenges that need to be solved regarding its use at an industrial scale, for example, improving its reaction selectivity, developing effective methods to separate the FRS and ILs, and alleviating the negative effect of the remaining ILs in FRS on subsequent ethanol fermentation. This editorial will give a brief discussion about opportunities and challenges of the acid catalyzed hydrolysis of LB in ILs for ethanol production.