Security Service or security service may refer to:
Government
Security agency, a nation's institution for intelligence gathering
List of security agencies (MI5, NSA, KGB, etc.)
Sicherheitsdienst (SD), Nazi German agency which translates as "Security Service"
MI5, also called the Security Service, the United Kingdom's counter-intelligence and security agency
United States Air Force Security Service, a former designation of the US Air Force Intelligence, Surveillance and Reconnaissance Agency
RCMP Security Service, the Royal Canadian Mounted Police's political intelligence branch
Swedish Security Service
Secret service, a government agency concerned with gathering intelligence data
Secret police, a police agency beyond the law to protect the political power of a dictator or regime
Other
Security service (telecommunication), security architecture for the interconnection of open systems
Security and Intelligence Services (India)
Private security company
Private military company