The list consists of effective collision strengths in the electron excitation (Upsilon) and de-excitation (Downsilon) with a kappa electron energy distribution as a function of the electron temperature and kappa for 10 forbidden transitions between the five lowest energy levels of the astronomically abundant doubly-ionized oxygen ion, O^2+^, in an intermediate coupling scheme using the Breit-Pauli relativistic terms as implemented in an R-matrix atomic scattering code (Berrington et al., 1995). An atomic target for the R-matrix scattering defined by 72 atomic terms is used in these calculations with Gailitis averaging in the region beneath thresholds where the effective quantum number is greater than 10. The raw collision strength data are obtained from a list created previously by the authors (Storey et al., 2014MNRAS.441.3028S, Cat. VI/141). The limits of the effective collision strength data are the same as the limits of the original raw collision strength data, that is the data apply for a temperature range between about 100-25000K with a free electron excitation energy up to about 1.3 Rydberg. These limits are adopted mainly for relevance to planetary nebulae and HII regions.