HCS may mean:
- Hackensack Christian School
- Hoboken Charter School
- Hallett Cove School in Adelaide, South Australia.
- Halifax Consciousness Scanner
- Hampton Christian Schools
- Holland Christian Schools
- Harlem Children Society
- Hartland Community School in Hartland, New Brunswick
- Hyderabad Civil Service
- Hard Clad Silica
- Harvard Computer Society
- Heritage Christian School (disambiguation), various institutions
- Hull Collegiate School in Anlaby, England.
- The High Compression Swirl engine by Ford in the 1980s
- Human Chorionic Somatomammotropin
- High-content screening
- Hierarchical cell structure
- Hydrocortisone or Cortisol, Which should not to be confused with Cortisone,a compound with a similar name, genesis and function
- Heliospheric current sheet
- Hummocky cross stratification
- Header Check Sequence
- Hereford Cathedral School
- Highland Cattle Society of Stirling, Scotland.
- High Carbon Steel
- Hinsdale Central School in Hinsdale, New York.
- Honorable Company's Ship, the prefix for a ship of the British East India Company (as in HCS Bombay)