DESI Legacy Imaging Surveys Data Release 9

We present the 9th Data Release of the DESI Legacy Imaging Surveys (LS DR9). Designed to provide faint extragalactic targets for the Dark Energy Spectroscopic Instrument's (DESI) cosmological survey, LS DR9 includes g, r and z-band data from the Dark Energy Camera Legacy Survey (DECaLS), the Beijing-Arizona Sky Survey (BASS), and the Mayall z-band Legacy Survey (MzLS), as well as public data from the Dark Energy Survey (DES). These surveys represent 1400 nights of observing on these three telescopes. DR9 covers a total area of 20,000 square degrees and achieves a nearly uniform depth within the DESI footprint. Images were processed with the NOAO Community Pipeline, and source detection and inference modeling with the Tractor algorithm. In addition to the optical photometric and morphological parameters, the LS DR9 catalogs present mid-infrared photometry at 3.4um, 4.5um, 12um, and 22um from new 7-year coadded WISE data. The catalogs contain 2 billion sources and will be publicly available from the legacysurvey.org website, NERSC, and NOIRLab's Astro Data Lab archives. Image-level products can be explored at legacysurvey.org/viewer .