Polysiphonia opaca
- kingdom: Plantae
- phylum: Rhodophyta
- class: Florideophyceae
- order: Ceramiales
- family: Rhodomelaceae
- genus: Polysiphonia
- species: Polysiphonia opaca
Cockburn Town
San Salvador
BahamasHamilton
Hamilton city
BermudaKey West
Florida
United States