We present version 8 of the CHIANTI database. This version includes a significant amount of new data and ions, mostly calculated with the R-matrix suite of codes by the UK APAP network. The new data represent a significant improvement in the soft X-ray, EUV and UV spectral regions, where several space missions are currently observing. In particular, all the coronal iron ions have improved atomic data, which affect the analyses of Hinode EIS and SDO/AIA data. New data for neutral and low charge states are also added. The data are assessed, but to improve the modelling of low-temperature plasma the effective collision strengths for the new datasets are not fitted as previously done. A change of format was needed for this purpose. A revised DEM package is also presented.