A detailed absorption cross section for molecular oxygen in the region of the Schumann-Runge bands has been calculated using data about the molecular constants for oxygen, the band strengths and linewidths for the Schumann-Runge system, and the absorption continua of oxygen in this region. The accuracy of the cross section is demonstrated by comparison with a range of experimental measurements. An absorption model for the mean transmission and effective local cross section for oxygen over 1.0-nm and 0.2-nm intervals in the wavelength region 175--205 nm has been based on the detailed cross section, and the coefficients of the model are given. The model incorporates an atmospheric temperature profile and is suitable for the calculation of photodissociation rates of oxygen and minor constituents in the atmosphere.