The 2023 release of the XMM OM Serendipitous Ultraviolet Source Survey (XMM-SUSS6.1) Catalog, a catalog of optical/UV sources detected by the Optical Monitor (OM) on-board the European Space Agency's (ESA's) XMM-Newton observatory, spans the period of observations from 2000 to November 2022. The data processing was performed at the European Space Astronomy Centre (ESAC, Madrid, Spain) using the XMM Science Analysis Software system (SAS) versions 18 and 19. In addition to covering a larger observation period, this sixth release reflects a change in philosophy with regard to the origin of the incorporated data. In previous releases, the data were generated via a bespoke processing of the OM Observation Data Files (ODFs) while in this new release, the catalog has been guided by the XMM user community and the authors have sought to harmonize the contents of the catalog with those of the OM data in the XMM-Newton Science Archive (XSA), which derive from the standard XMM-Newton pipeline processing system. While the bespoke processing and pipeline systems are fundamentally very similar, they are not identical and the differences lead to some differences in the output. The number of observations (OBSIDs) included in the catalog is 12,057. This table (XMMOMSUOB) contains the list of these observations and their characteristics, giving for each observation the filters used, the exposure time for each filter, the number of sources detected in each filter and the detection magnitude limit for each filter. The total number of entries in this release is 9,920,390. They correspond to 6,659,554 unique sources, of which 1,225,117 have multiple entries in the source table, corresponding to different observations. This list of sources is available at the HEASARC as the <a href="/W3Browse/xmm-newton/xmmomsuss.html">XMMOMSUSS table</a>. The documentation on the first release of this catalog is available at <a href="http://www.mssl.ucl.ac.uk/www_astro/XMM-OM-SUSS/Summary.shtml">http://www.mssl.ucl.ac.uk/www_astro/XMM-OM-SUSS/Summary.shtml</a>;. This HEASARC database table contains the sixth release of the XMM-OM SUSS catalog, XMM-SUSS6.1, released by ESA in October 2023, obtained from the XMM-Newton Science Archive (<a href="http://xmm.esac.esa.int/xsa">http://xmm.esac.esa.int/xsa</a>;), and ingested into the HEASARC database in October 2023. It is also available at the HEASARC as the gzipped FITS file <a href="https://heasarc.gsfc.nasa.gov/FTP/xmm/data/catalogues/XMM-OM-SUSS6-1.1.fits.gz">https://heasarc.gsfc.nasa.gov/FTP/xmm/data/catalogues/XMM-OM-SUSS6-1.1.fits.gz</a>;. This is a service provided by NASA HEASARC .
