We present analytic representation of dielectric function (ɛ ═ ɛ1 + iɛ₂) data from 1.7 to 5.0 eV for the temperature from 300 to 803 K of oxide-free AlSb that are the closest representation to date of the intrinsic bulk dielectric response ɛ of the material. Pseudodielectric functions 'ɛ' were measured on a 1.5 µm thick film grown on (001) GaAs by molecular beam epitaxy. Data were obtained with the film in situ to avoid surface oxidation artifacts. The dielectric function parametric model and multilayer calculation were performed to obtain pure dielectric function and fundamental bandgap (E0) of the AlSb film. The ɛ spectrum was successfully reconstructed by seven polynomials and a pole, which can be used to determine ɛ for arbitrary temperatures. Our results should be useful for device design based on AlSb.