Pointed observations with XMM-Newton provide the basis for creating catalogues of X-ray sources detected serendipitously in each field. This paper describes the creation and characteristics of the 2XMM catalogue. The 2XMM catalogue has been compiled from a new processing of the XMM-Newton EPIC camera data. The main features of the processing pipeline are described in detail. The catalogue, the largest ever made at X-ray wavelengths, contains 246897 detections drawn from 3491 public XMM-Newton observations over a 7-year interval, which relate to 191870 unique sources. The catalogue fields cover a sky area of more than 500deg^2^. The non-overlapping sky are a is ~360deg^2^ (~1% of the sky) as many regions of the sky are observed more than once by XMM-Newton. The catalogue probes a large sky area at the flux limit where the bulk of the objects that contribute to the X-ray background lie and provides a major resource for generating large, well-defined X-ray selected source samples, studying the X-ray source population and identifying rare object types. The main characteristics of the catalogue are presented, including its photometric and astrometric properties The 2XMMi catalogue is available as Cat. <IX/40> in VizieR.