The Freedom of Information Act (FOIA /ˈfɔɪjə/ FOY-yə), 5 U.S.C. § 552, is the United States federal freedom of information law that requires the full or partial disclosure of previously unreleased or uncirculated information and documents controlled by the U.S. government upon request. The act defines agency records subject to disclosure, outlines mandatory disclosure procedures, and includes nine exemptions that define categories of information not subject to disclosure. The act was intended to make U.S. government agencies' functions more transparent so that the American public could more easily identify problems in government functioning and put pressure on Congress, agency officials, and the president to address them. The FOIA has been changed repeatedly by both the legislative and executive branches.

The FOIA is commonly known for being invoked by news organizations for reporting purposes, though such uses make up less than 10% of all requests—which are more frequently made by businesses, law firms, and individuals.

As indicated by its long title, the Freedom of Information Act (FOIA) was moved from its original home in Section 3 of the Administrative Procedure Act (APA). Section 3 of the APA, as enacted in 1946, gave agencies broad discretion concerning the publication of governmental records. Following concerns that the provision had become more of a withholding than a disclosure mechanism, Congress amended the section in 1966 as a standalone act to implement "a general philosophy of full agency disclosure". The amendment required agencies to publish their rules of procedure in the Federal Register, 5 U.S.C. § 552(a)(1)(C), and to make available for public inspection and copying their opinions, statements of policy, interpretations, and staff manuals and instructions that are not already published in the Federal Register, § 552(a)(2). In addition, § 552(a)(3) requires every agency, "upon any request for records which ... reasonably describes such records" to make such records "promptly available to any person". By § 552(a)(4)(B) if an agency improperly withholds any documents, the district court has jurisdiction to order their production. Unlike the review of other agency action that must be upheld if supported by substantial evidence and not arbitrary or capricious, FOIA expressly places the burden "on the agency to sustain its action", and directs the district courts to "determine the matter de novo".^{[citation needed]}

With the ongoing stress on both constitutional and inherent rights of American citizens and the added assertion of government subservience to the individual, some, particularly representative John E. Moss, thought that it was necessary for government information to be available to the public. This push built on existing principles and protocols of government administration already in place.

Although some officials, including President Lyndon B. Johnson, believed certain unclassified government information should remain confidential, Congress moved to increase transparency. In 1966, despite opposition from the White House, Congress expanded Section 3 of the Administrative Procedure Act to promote the public's right to access government records. The Privacy Act of 1974 was later enacted to protect personal information held by the government.

The act explicitly applies only to government agencies under the executive branch. These agencies are required by several mandates to comply with public solicitation of information. Along with making public and accessible all bureaucratic and technical procedures for applying for documents from that agency, agencies are also subject to penalties for hindering the process of a petition for information. According to the act, if "agency personnel acted arbitrarily or capriciously with respect to the withholding, the Special Counsel shall promptly initiate a proceeding to determine whether disciplinary action is warranted against the officer or employee who was primarily responsible for the withholding." In this way, there is recourse for one seeking information to go to a federal court if suspicion of illegal tampering or delayed sending of records exists. However, nine exemptions address issues of sensitivity and personal rights. They are (as listed in 5 U.S.C. § 552):

The Postal Reorganization Act of 1970 (at 39 U.S.C. § 410(c)(2)) exempts the U.S. Postal Service from disclosure of "information of a commercial nature, including trade secrets, whether or not obtained from a person outside the Postal Service, which under good business practice would not be publicly disclosed".

A federal court has concisely described the vital role of the FOIA in democracy: