6061 20240108165803.0 10.1051/0004-6361/202243688 DOI SCART-2023-0022 Creevey, O. L. Gaia Data Release 3: Astrophysical parameters inference system (Apsis) I -- methods and content overview 2023 Gaia Data Release 3 contains a wealth of new data products for the community. Astrophysical parameters are a major component of this release. They were produced by the Astrophysical parameters inference system (Apsis) within the Gaia Data Processing and Analysis Consortium. The aim of this paper is to describe the overall content of the astrophysical parameters in Gaia DR3 and how they were produced. In Apsis we use the mean BP/RP and mean RVS spectra along with astrometry and photometry, and we derive the following parameters: source classification and probabilities for 1.6 billion objects, interstellar medium characterisation and distances for up to 470 million sources, including a 2D total Galactic extinction map, 6 million redshifts of quasar candidates and 1.4 million redshifts of galaxy candidates, along with an analysis of 50 million outlier sources through an unsupervised classification. The astrophysical parameters also include many stellar spectroscopic and evolutionary parameters for up to 470 million sources. These comprise Te, log g, and [M/H] (470 million using BP/RP, 6 million using RVS), radius (470 million), mass (140 million), age (120 million), chemical abundances (up to 5 million), diffuse interstellar band analysis (0.5 million), activity indices (2 million), Halpha equivalent widths (200 million), and further classification of spectral types (220 million) and emission-line stars (50 thousand). This paper is part of a series of three papers: this Paper I focusses on describing the global content of the parameters in Gaia DR3. The accompanying papers II and III focus on the validation and use of the stellar and non-stellar products, respectively. This catalogue is the most extensive homogeneous database of astrophysical parameters to date, and it is based uniquely on Gaia data. It will only be superseded in Gaia Data Release 4. This catalogue will therefore remain a key reference over the next four years, providing astrophysical parameters independent of other ground- and space-based data. Gaia PRODEX/ Gaia PRODEX/ Gaia PRODEX NO methods: data analysis catalogs stars: fundamental parameters ISM: general Galaxy: stellar content galaxies: fundamental parameters Sordo, R. Pailler, F. Frémat, Y. Heiter, U. Thévenin, F. Andrae, R. Fouesneau, M. Lobel, A. Bailer-Jones, C. A. L. Garabato, D. Bellas-Velidis, I. Brugaletta, E. Lorca, A. Ordenovic, C. Palicio, P. A. Sarro, L. M. Delchambre, L. Drimmel, R. Rybizki, J. Torralba Elipe, G. Korn, A. J. Recio-Blanco, A. Schultheis, M. S. De Angeli, F. Montegriffo, P. Abreu Aramburu, A. Accart, S. Álvarez, M. A. Bakker, J. Brouillet, N. Burlacu, A. Carballo, R. Casamiquela, L. Chiavassa, A. Contursi, G. Cooper, W. J. Dafonte, C. Dapergolas, A. de Laverny, P. Dharmawardena, T. E. Edvardsson, B. Le Fustec, Y. García-Lario, P. García-Torres, M. Gomez, A. González-Santamaría, I. Hatzidimitriou, D. Jean-Antoine Piccolo, A. Kontizas, M. Kordopatis, G. Lanzafame, A. C. Lebreton, Y. Licata, E. L. Lindstrøm, H. E. P. Livanou, E. Magdaleno Romeo, A. Manteiga, M. Marocco, F. Marshall, D. J. Mary, N. Nicolas, C. Pallas-Quintela, L. Panem, C. Pichon, B. Poggio, E. Riclet, F. Robin, C. Santoveña, R. Silvelo, A. Slezak, I. Smart, R. L. Soubiran, C. Süveges, M. Ulla, A. Utrilla, E. Vallenari, A. Zhao, H. Zorec, J. Barrado, D. Bijaoui, A. Bouret, J. -C. Blomme, R. Brott, I. Cassisi, S. Kochukhov, O. Martayan, C. Shulyak, D. Silvester, J. Astronomy & Astrophysics 674 2023 A26 (35pp) ronny.blomme@observatoire.be https://ui.adsabs.harvard.edu/abs/2022arXiv220605864C/abstract https://arxiv.org/abs/2206.05864 published in REFERD