We present the first data release of the James Clerk Maxwell Telescope Plane Survey (JPS), the JPS Public Release 1. JPS is an 850-mu m continuum survey of six fields in the northern inner Galactic plane in a longitude range of l = 7 degrees - 63 degrees, made with the Submillimetre Common-User Bolometer Array 2. This first data release consists of emission maps of the six JPS regions with an average pixel-to-pixel noise of 7.19 mJy beam(-1), when smoothed over the beam, and a compact source catalogue containing 7813 sources. The 95 per cent completeness limits of the catalogue are estimated at 0.04 Jy beam(-1) and 0.3 Jy for the peak and integrated flux densities, respectively. The emission contained in the compact source catalogue is 42 +/- 5 per cent of the total and, apart from the large-scale (greater than 8 arcmin) emission, there is excellent correspondence with features in the 500-mu m Herschel maps. We find that, with two-dimensional matching, 98 +/- 2 per cent of sources within the fields centred at l = 20 degrees, 30 degrees, 40 degrees and 50. are associated with molecular clouds, with 91 +/- 3 per cent of the l = 30 degrees and 40 degrees sources associated with dense molecular clumps. Matching the JPS catalogue to Herschel 70-mu m sources, we find that 38 +/- 1 per cent of sources show evidence of ongoing star formation. The JPS Public Release 1 images and catalogue will be a valuable resource for studies of star formation in the Galaxy and the role of environment and spiral arms in the star formation process.