Sponges form symbioses with a vast array of taxa, but many interactions are only known from a few exemplar species and remain poorly understood. Determining the range of species combinations of hosts and symbionts establishes the foundation for further investigation, defines the specificity of the interactions, and provides hints about what the adaptive significance of the interactions might be. Symbioses between coral reef sponges and zoanthids of the genera Parazoanthus and Epizoanthus are widespread (from Brazil to Bermuda, and Belize to Barbados), common (able to colonize all host individuals in a population), and have been known in a few systematically disparate but numerically abundant sponge host species for more than a century. However, the extent of the diversity of species interactions on a region-wide scale had not been examined. To explore the diversity of symbiotic combinations, I have compiled spongezoanthid species combinations as 1) reported in the sponge and zoanthid taxonomic literature; 2) captured in the collections of the United States National Museum of Natural History; and 3) observed in field surveys conducted in Panama, the United States (Florida, Georgia, and Navassa Island), Dominica, Barbados, and Tobago. The results indicate that more than 70 sponge species (representing 7 orders) host at least 7 species of zoanthid across the central western Atlantic region. The patterns of sponge-zoanthid species combinations demonstrate that 1) sponges are highly specific to zoanthid species, 2) zoanthids are not specific to sponge species, however 3) zoanthids are specific to sponge higher taxa.