In this data release from the ongoing LOw-Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) we present 120-168\,MHz images covering 27\% of the northern sky. Our coverage is split into two regions centred at approximately 12h45m +44$^\circ$30$\arcmin$ and 1h00m +28$^\circ$00$\arcmin$ and spanning 4178 and 1457 square degrees respectively. The images were derived from 3,451\,hrs (7.6\,PB) of LOFAR High Band Antenna data which were corrected for the direction-independent instrumental properties as well as direction-dependent ionospheric distortions during extensive, but fully automated, data processing. A catalogue of 4,396,228 radio sources is derived from our total intensity (Stokes I) maps, where the majority of these have never been detected at radio wavelengths before. At 6$\arcsec$ resolution, our full bandwidth Stokes I continuum maps with a central frequency of 144\,MHz have: a median rms sensitivity of 83\,$\mu$Jy/beam; a flux density scale accuracy of approximately 10\%; an astrometric accuracy of 0.2$\arcsec$; and we estimate the point-source completeness to be 90\% at a peak brightness of 0.8\,mJy/beam. By creating three 16\,MHz bandwidth images across the band we are able to measure the in-band spectral index of many sources, albeit with an error on the derived spectral index of $>\pm0.2$ which is a consequence of our flux-density scale accuracy and small fractional bandwidth. Our circular polarisation (Stokes V) 20$\arcsec$ resolution 120-168\,MHz continuum images have a median rms sensitivity of 95\,$\mu$Jy/beam, and we estimate a Stokes I to Stokes V leakage of 0.056\%. Our linear polarisation (Stokes Q and Stokes U) image cubes consist of $480 \times 97.6$\,kHz wide planes and have a median rms sensitivity per plane of 10.8\,mJy/beam at 4$\arcmin$ and 2.2\,mJy/beam at $20\arcsec$; we estimate the Stokes I to Stokes Q/U leakage to be approximately 0.2\%. Here we characterise and publicly release our Stokes I, Q, U and V images in addition to the calibrated $uv$-data to facilitate the thorough scientific exploitation of this unique dataset.
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