There are currently 57 Offices of the Inspector General (OIG) in various Executive departments and agencies of the US Federal government. The OIGs were established by the Inspector General Act of 1978 to investigate waste, fraud and abuse. They investigate both criminal and civil matters.

28 OIGs have special agents, who are law enforcement officers who carry weapons and have the power of arrest. The scope of most OIGs is generally fairly narrow, and is limited to fraud investigation and executive protection for the head of their parent organisation. However, that responsibility can reach further than one might expect - for instance, the Department of Agriculture OIG investigates welfare fraud and employs 217 agents. Some OIGs simply fulfil their traditional role, while another agency in that department performs the primary law enforcement role. In the United States Postal Service, the OIG investigates fraud against the service, while the US Postal Inspection Service investigates crimes that involve the mail.

In 1987, the OIG community began teaching Inspector General Basic Training Program (IG Basic) at Federal Law Enforcement Training (FLETC) . IG Basic taught graduates of FLETC's Criminal Investigator Training Program (CITP) specialised investigative techniques that particularly applied to the OIGs. This was superseded in 1999 when the Inspector General community formed the Inspector General Academy at FLETC to train OIG special agents and other employees in a variety of basic and advanced courses.