This dataset contains a polychaete database, constructed from extensive studies carried out on the continental shelf (<200 m depth) of the Southern Gulf of Mexico (18° 30′–22° 20′ N; 89° 41′–97° 4′ W). S samples were collected during six oceanographic expeditions, on board the R/V “Justo Sierra” (Universidad Nacional Autónoma de México), from 1988 to 1996, as part of two institutional projects “IMCA” and “DINAMO” [55]. The collected specimens from 61 stations were identified to species level and deposited in the “Colección Nacional de Anélidos Poliquetos” from the Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México (CNAP-ICML, UNAM; DFE.IN.061.0598). The database includes information on all identified polychaete species, the geographical position of the sampling stations (latitude and longitude), and environmental variables (sediment composition, depth, temperature, and salinity). In addition, the taxonomic information was carefully checked. We verified the validity of names and synonymies and omitted species whose taxonomic identification was doubtful. We used the more recent systematic reviews and the World Polychaeta Database accessed through the World Register of Marine Species (WORMS) database.