HCS
- East India Company
- HCS clustering algorithm
- Hackensack Christian School
- Hajdu–Cheney syndrome
- Halifax Choral Society
- Hallett Cove School
- Halo Championship Series
- Hampshire Country School
- Hampton Christian Schools
- Hard-clad silica optical fiber
- Hardin County Schools
- Harlem Children Society
- Harrisburg Christian School
- Hawkins County Schools
- Header check sequence
- Healthcare scientist
- Heliospheric current sheet
- Henry Christian Spencer
- Hereford Cathedral School
- Heritage Christian School (disambiguation)
- Heritage College Sydney
- Hierarchical cell structure (telecommunications)
- Hierarchical constraint satisfaction
- High Council of State (disambiguation)
- High-content screening
- Highland Catholic School
- Hilltop Christian School
- Hinsdale Central School
- Holland Christian Schools
- Hollywood Center Studios
- Holy Cross School (disambiguation)
- Honoris Crux Silver
- Hooghly Collegiate School
- Horry County Schools
- Hub-center steering
- Hull Collegiate School
- Human chorionic somatomammotropin
- Hummocky cross-stratification
- Hyderabad Civil Service
- Hydrocortisone
- Sensitive compartmented information
- The Histochemical Society