The Javalambre-Photometric Local Universe Survey (J-PLUS ) is an ongoing 12-band photometric optical survey, observing thousands of square degrees of the Northern hemisphere from the dedicated JAST/T80 telescope at the Observatorio Astrofísico de Javalambre (OAJ). T80Cam is a 2 deg2 field-of-view camera mounted on this 83 cm-diameter telescope, and is equipped with a unique system of filters spanning the entire optical range (3 500–10 000 Å). This filter system is a combination of broad, medium and narrow-band filters, optimally designed to extract the rest-frame spectral features (the 3 700–4 000 Å Balmer break region, Hd, Ca H+K, the G-band, the Mgb and Ca triplets) that are key to both characterize stellar types and to deliver a low-resolution photospectrum for each pixel of the sky observed. With a typical depth of AB ~ 21.25 mag per band, this filter set thus allows for an indiscriminate and accurate characterization of the stellar population in our Galaxy, it provides an unprecedented 2D photo-spectral information for all resolved galaxies in the local universe, as well as accurate photo-z estimates (at the ¿ z ~ 0.01–0.03 precision level) for moderately bright (up to r ~ 20 mag) extragalactic sources. While some narrow band filters are designed for the study of particular emission features ([OII]/¿3727, Ha/¿6563) up to z < 0.015, they also provide well-defined windows for the analysis of other emission lines at higher redshifts. As a result, J-PLUS has the potential to contribute to a wide range of fields in Astrophysics, both in the nearby universe (Milky Way structure, globular clusters, 2D IFU-like studies, stellar populations of nearby and moderate redshift galaxies, clusters of galaxies) and at high redshifts (emission line galaxies at z ˜ 0.77, 2.2 and 4.4, quasi stellar objects, etc). With this paper, we release ~36 deg2 of J-PLUS data, containing about 1.5 × 105 stars and 105 galaxies at r < 21 mag. These numbers are expected to rise to about 35 million of stars and 24 million of galaxies by the end of the survey

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