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{deg}-63{deg}, 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 7.19mJy/beam, 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 0.04Jy/beam and 0.3Jy 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 {\pm} 2 per cent of sources within the fields centred at l=20{deg}, 30{deg}, 40{deg} and 50{deg} are associated with molecular clouds, with 91+/-3 per cent of the l=30{deg} and 40{deg} 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.