The State Security Service, also known by its original name as the Directorate for State Security, was the national secret police intelligence and security agency of Socialist Federal Republic of Yugoslavia (SFR Yugoslavia). It was at all times best known by the acronym UDBA, which is derived from the organization's original name in the Serbo-Croatian language: "Uprava državne bezbednosti" ("Directorate for State Security").

The acronyms SDB (Serbian) or SDS (Croatian) were used officially after the organization was renamed into "State Security Service". In its latter decades it was composed of eight semi-independent secret police organizations—one for each of the six Yugoslav federal republics and two for the autonomous provinces—coordinated by the central federal headquarters in the capital of Belgrade.

Although it operated with more restraint than secret police agencies in the communist states of Eastern Europe, the UDBA was a feared tool of control. It is alleged that the UDBA was responsible for the "eliminations"^{[clarification needed]} of thousands of enemies of the state within Yugoslavia and internationally (estimates about 200 assassinations and kidnappings). Eliminations vary from those during World War II of the Ustaše Croat fascist leader Vjekoslav Luburić in Spain, to Croatian emigrant writer Bruno Bušić and Serbian emigrant writer Dragiša Kašiković, although war criminals have to be distinguished from those assassinated only for dissent or political reasons.

With the breakup of Yugoslavia, the breakaway republics went on to form their own secret police agencies, while the Serbian State Security Directorate kept its UDBA-like name.

From its founding in 1946, the secret police organization originally held the name "Directorate for State Security". In Yugoslavia the predominant administrative language on the federal level was the Serbo-Croatian language, and more specifically the Serbian variant thereof: therein the name was Uprava državne bezbednosti ("Управа државне безбедности" in the coequal Cyrillic script). From this was derived the acronym "UDB", or, less formally and accurately: "UDBA". "UDBA" (pronounced as a single word and not an acronym), was the most common colloquial name for the organization throughout its history.

After 20 years, in 1966, with the political downfall of its hardliner chief, Aleksandar Ranković, the organization was renamed to the "State Security Service", which (in the Serbian variant of Serbo-Croatian) is Služba državne bezbednosti (Служба државне безбедности), with the corresponding acronym SDB. Even though that would be its name for the remaining 28 years of Yugoslavia's existence, it never stopped being mainly known as "(the) UDBA". Even after it was (at least formally) decentralized in 1967 into 8 semi-independent organizations each answering to an individual federal entity.

UDBA formed a major part of the Yugoslav intelligence services from 1946 to 1991, and was primarily responsible for internal state security. After 1946 the UDBA underwent numerous security and intelligence changes due to topical issues at that time, including: fighting gangs; protection of the economy; Cominform/Informbiro; and bureaucratic aspirations. In 1945 and 1946, for instance, the UDBA was organized into districts. In 1950, when the administrative-territorial units were abolished as authorities, the UDBA was reorganized again. During this period the intelligence and security activities concentrated less on intelligence and more on internal security. There was an emphasis on collectivism, brotherhood, social harmony, loyalty, and tolerance towards those with different views. Deviation from this set of values became an immediate issue for security services.

Later, the use of force was mitigated and when the process of "decentralization of people's power" began, intelligence and security services underwent further reorganization in order to decentralise power and increase effectiveness. At the plenum of the Central Committee in July 1966, the political leadership accused the SDB of hindering reforms towards self-administration. As a result, the SDB was decentralized, its personnel reduced (especially on the federal level) and control commissions established. New regulations were issued, strengthening the independent initiative of the state security services of the six Yugoslav republics and the autonomous provinces. The SDB was deprived of executive functions and entrusted with identifying and preventing hostile activities. The Act on Internal Affairs and the Decree on Organization of State Internal Affairs Secretariat regulated the intelligence security authority as the prerogative of the State Security Directorate within the Ministry of the Interior. The following reorganization addressed issues relating to the competence of the federation (state security, cross-border traffic, foreign citizens, passports, introduction and dissemination of foreign press, and federal citizenship).