The Unlawful Internet Gambling Enforcement Act of 2006 (UIGEA) is a United States federal law that prohibits financial transactions related to unlawful internet gambling. Enacted as Title VIII of the SAFE Port Act (which primarily focused on port security), it was signed into law by President George W. Bush on October 13, 2006. The legislation targets gambling businesses, making it illegal for them to knowingly accept payments in connection with bets or wagers conducted via the internet that violate any federal or state laws. It does not criminalize online gambling itself but focuses on the financial mechanisms that support it, effectively restricting the ability of offshore and domestic gambling operators to receive funds from U.S. customers through banks, credit cards, and other payment systems.

The UIGEA includes specific exemptions for certain activities, such as fantasy sports that meet defined criteria (e.g., involving a predetermined number of participants and not based on current events outcomes in a single contest), skill-based games, and legal intrastate and intertribal gaming. It remains ambiguous on state lotteries and interstate horse racing wagers, leading to ongoing debates and legal interpretations. Enforcement has been handled primarily by the Department of Justice and financial regulators like the Federal Reserve, with significant impacts on the online gambling industry, including the shutdown of major poker sites like PokerStars and Full Tilt Poker in 2011 following investigations into violations.

The law has faced criticism for its broad scope, potential overreach into state-regulated activities, and for driving gambling operations underground rather than eliminating them, while supporters argue it protects consumers from fraud and addiction risks associated with unregulated online betting. Over the years, the UIGEA has influenced subsequent legislation, such as the 2018 repeal of the Professional and Amateur Sports Protection Act (PASPA), which opened the door to legalized sports betting in many states. However, it continues to shape the landscape of internet gambling enforcement, with ongoing challenges related to cryptocurrency transactions and evolving technology. The act's implementation has involved interagency cooperation, including guidance from the Financial Crimes Enforcement Network (FinCEN), and has been subject to lawsuits and regulatory clarifications, highlighting tensions between federal oversight and state autonomy in gaming policy.