HCS may refer to:

Education

• Hackensack Christian School, in New Jersey, United States
• Hallett Cove School, in Adelaide, South Australia
• Hampshire Country School, in New Hampshire, United States
• Hampton Christian Schools, in Virginia, United States
• Hardin County Schools, in Kentucky, United States
• Harrisburg Christian School, in Pennsylvania, United States
• Hereford Cathedral School, in England
• Heritage Christian School (disambiguation)
• Heritage College Sydney, in New South Wales, Australia
• Highland Catholic School, in Minnesota, United States
• Hilltop Christian School, in North Carolina, United States
• Hinsdale Central School, in New York, United States
• Hooghly Collegiate School, in West Bengal, India
• Holland Christian Schools, in Michigan, United States
• Holy Cross School (disambiguation)
• Horry County Schools, in South Carolina, United States
• Hull Collegiate School, in England

Biology and medicine

• Hajdu–Cheney syndrome
• High-content screening
• Human chorionic somatomammotropin
• Hydrocortisone

Science and mathematics

• HCS clustering algorithm
• Heliospheric current sheet
• Hierarchical constraint satisfaction
• Hummocky cross-stratification

Technology

• Hard-clad silica optical fiber
• Header check sequence
• Hierarchical cell structure (telecommunications)
• Hub-center steering

Other uses

• Halifax Choral Society
• Halo Championship Series
• Harlem Children Society
• High Council of State (disambiguation)
• The Histochemical Society
• Hollywood Center Studios
• Honoris Crux Silver, a military decoration of South Africa
• Honourable Company's Service or Honourable Company's Ship, used to prefix the names of East India Company ships
• HUMINT Control System, an aspect of the Sensitive compartmented information protocol
• Hyderabad Civil Service, India