New generation spacecraft technology requires more and more deployable, light-weight, thin polymer ?lms, in particularnovelpolyimidematerialswithhighopticaltransparency,excellentfoldabilityandsuperior ?exibility. In this work, we develop a highly transparent, ultra-foldable, ultra-?exible and ultra-processable polyimide composite material by incorporating 5–8wt% of ionic liquid 1-ethyl-3-methylimidazolium bis((tri?uoromethyl) sulfonyl)imide into colorless polyimide matrices. This 23-μm-thick polyimide composite ?lm exhibits a high optical transmittance of 90.4% even at 450nm wavelength and an incredibly low cuto? wavelength of 273nm. It is an extremely strong and ?exible material, with a tensile modulus of 844.6MPa, a tensile strength of 48.2MPa, a high elongation at break of 108.4%, and an extraordinary minimum bend radius of 1μm. It can be easily folded in half 4 times or twisted by 900° without any crack damages. Moreover, it has a low expense cost and good ?lm processability for industrialization manufacturing. All of these superior performances render this ionic liquid/polyimide composite an ideal structural material for solar sails, solar arrays and thin-?lm photovoltaics, etc.