The 3XMM-DR7 catalogue contains source detections drawn from 9710 XMM-Newton EPIC observations, covering an energy interval from 0.2 keV to 12 keV. These observations were made between 2000 February 3 and 2016 December 15 and all datasets were publicly available by 2016 December 31, but not all public observations are included in this catalogue This version of the XMM-Newton EPIC Serendipitous Source Catalogue, 3XMM-DR7 includes 596268 clean detections which relate to 499266 unique sources from 9710 observations that were public by the 31st January 2016. 3XMM-DR7 covers a total sky area of ~1032 square degrees if overlaps are taken into account, where some regions of the sky have been pointed as many as 50 times. The median flux in the total photon energy band (0.2 - 12 keV) of the catalogue detections is ~ 1.9 × 10-14 erg cm-2 s-1; in the soft energy band (0.2 - 2 keV) the median flux is ~ 6 × 10-15, and in the hard band (2 - 12 keV) it is ~ 8 × 10-15. About 23% of the sources have total fluxes below 1 × 10-14 erg cm-2 s-1.