HCSS may refer to:
- Holy Cross Secondary School in Peterborough, Ontario
- Hypercompact stellar system, a cluster of stars around a supermassive black hole
- The file extension ".hcss" (Hyper Color Swatch Set) associated with the "Hyper Color" software application from SodaBush
Hardcore Superstar, a Swedish rock band.
- HCSS (album), 2015 album by Hardcore Superstar above