The Financial Crimes Enforcement Network (FinCEN) is a bureau within the United States Department of the Treasury that collects and analyzes information about financial transactions to combat domestic and international money laundering, terrorist financing, and other financial crimes.

FinCEN's stated mission is to "safeguard the financial system from illicit activity, counter money laundering and the financing of terrorism, and promote national security through strategic use of financial authorities and the collection, analysis, and dissemination of financial intelligence." FinCEN serves as the U.S. Financial Intelligence Unit (FIU) and is one of 147 FIUs making up the Egmont Group of Financial Intelligence Units. FinCEN's self-described motto is "follow the money." It is a network bringing people and information together, by coordinating information sharing with law enforcement agencies, regulators and other partners in the financial industry.

FinCEN was established by Treasury Order 105-08 on April 25, 1990. In May 1994, its mission expanded to involve regulatory responsibilities. In October 1994, Treasury's Office of Financial Enforcement merged with FinCEN. On September 26, 2002, after passage of Title III of the PATRIOT Act, Treasury Order 180-01 designated FinCEN as an official bureau within the Department of the Treasury.

Since 1995, FinCEN has employed the FinCEN Artificial Intelligence System (FAIS).

In September 2012, FinCEN's information technology called FinCEN Portal and Query System, migrated with 11 years of data into FinCEN Query, a search engine similar to Google. It is a "one stop shop" [sic] accessible via the FinCEN Portal allowing broad searches across more fields than before and returning more results. Since September 2012 FinCEN generates 4 new reports: Suspicious Activity Report (SAR), Currency Transaction Report (CTR), the Designation of Exempt Person (DOEP), and Registered Money Service Business (RMSB).

As of November 2013, FinCEN employed approximately 340 people, mostly intelligence professionals with expertise in the financial industry, illicit finance, financial intelligence, the AML/CFT (anti-money laundering / combating the financing of terrorism) regulatory regime, computer technology, and enforcement". The majority of the staff are permanent FinCEN personnel, with about 20 long-term detailees assigned from 13 different regulatory and law enforcement agencies. FinCEN shares information with dozens of intelligence agencies, including the Bureau of Alcohol, Tobacco, and Firearms; the Drug Enforcement Administration; the Federal Bureau of Investigation; the U.S. Secret Service; the Internal Revenue Service; the Customs Service; and the U.S. Postal Inspection Service.

The 2001 USA PATRIOT Act required the Secretary of the Treasury to create a secure network for the transmission of information to enforce the relevant regulations. FinCEN's regulations under Section 314(a) enable federal law enforcement agencies, through FinCEN, to reach out to more than 45,000 points of contact at more than 27,000 financial institutions to locate accounts and transactions of persons that may be involved in terrorist financing and/or money laundering. A web interface allows the person(s) designated in §314(a)(3)(A) to register and transmit information to FinCEN. The partnership between the financial community and law enforcement allows disparate bits of information to be identified, centralized, and rapidly evaluated.

In 2003, FinCEN disseminated information on "informal value transfer systems" (IVTS), including hawala, a network of people receiving money for the purpose of making the funds payable to a third party in another geographic location, generally taking place outside of the conventional banking system through non-bank financial institutions or other business entities whose primary business activity may not be the transmission of money. On September 1, 2010, FinCEN issued a guidance on IVTS referencing United States v. Banki and hawala.