An analytic expression of the dielectric function of monolayer molybdenum disulfide (MoS2) epsilon = epsilon(1) + i epsilon(2) is presented for energies from 1.4 to 6.0 eV and temperatures from 35 to 350 K. The dielectric function parametric model is used to express epsilon as a sum of polynomials, which naturally includes asymmetry of critical-point lineshapes. The temperature dependence is achieved by fitting model parameters. In this way, the dielectric function of MoS2 for arbitrary temperature can be calculated. We observed the fundamental absorption peak, which occurs at the K point of the Brillouin zone. These results are expected to be useful in designing and understanding applied-device technologies based on monolayer MoS2.