Sponges are recognized as a diverse and abundant component of mesophotic and deep-sea ecosystems worldwide. In Flower Garden Banks National Marine Sanctuary region within the northwestern Gulf of Mexico, sponges thrive among diverse biological and geological habitats between 16-200+ m deep (i.e., coral reefs and communities, algal nodule and coralline algae reefs, mesophotic reefs, patch reefs, scarps, ridges, soft substrate, and rocky outcrops). We present a synoptic guide developed by studying common sponge species in the region, through direct sampling and in situ photographic records.  A total of 63 species are included: 60 are Demospongiae (14 orders), 2 are Hexactinellida (1 order), 2 are Homoscleromorpha (1 order). Thirty-nine taxa are identified to species and 11 were identified to have affinity with, but are not identical to, a known species. Thirteen taxa could only be identified to genus level at this time, and the species remain as uncertain (incerta sedis), with the potential to constitute new species or variants of known species. One specimen received only a family assignation.  This study extends geographic or mesophotic occurrence data for 11 known species and includes several potentially new species. This work improves our knowledge of Gulf of Mexico sponge biodiversity and highlights the importance of the region for scientists and resource managers.