With the depletion of resources, biomass becomes a promising source of chemicals and fuels, currently obtained from petroleum. Cellulose is the most abundant material produced in earth, but it is difficult to dissolve which makes its transformation limited. Dissolution of cellulose requires severe temperature, non-conventional solvents and/or extreme acid or basic conditions. Thus, its processing is very pollutant. Ionic liquids are presented as clean solvents for cellulose. These are substances composed entirely of ions that are liquid at room temperature. Among other interesting properties, ionic liquids are non volatile and they are good solvents for a number of substances. Processes for cellulose processing in ionic liquids have been patented for several applications, the most important being: pre-treatment for biomass prior to fermentation for bio-ethanol production, hydrolysis for obtaining chemicals from biomass and substitution reaction for obtaining derivatives of cellulose and other natural polymers.