United States Customs and Border Protection (CBP) is the largest federal law enforcement agency of the United States Department of Homeland Security. It is the country's primary border control organization, charged with regulating and facilitating international trade, collecting import duties, as well as enforcing U.S. regulations, including trade, customs, and immigration. CBP is one of the largest law enforcement agencies in the United States. It has a workforce of more than 45,600 federal agents and officers. It is headquartered in Washington, D.C.

The CBP has a workforce of over 58,000 employees, including officers and agents, agriculture specialists, aircraft pilots, trade specialists, mission support staff, and canine enforcement officers and agents.

There are 328 officially designated ports of entry and an additional 14 pre-clearance locations. CBP is also in charge of the Container Security Initiative, which identifies and inspects foreign cargo in its mother country before it is to be imported into the United States. In addition the CBP claims to have legal jurisdiction to conduct some activities up to 100 miles (160 km) inwards from any land or sea border. This can include operating interior checkpoints.

CBP assess all passengers flying into the U.S. for terrorist risk via the Joint Terrorism Task Force (JTTF) and systems such as Advance Passenger Information System (APIS), United States Visitor and Immigrant Status Indication Technology (US-VISIT), and the Student and Exchange Visitor System (SEVIS). CBP also works with the U.S. Food and Drug Administration to screen high-risk imported food shipments in order to prevent bio-terrorism and agro-terrorism.

Through the Container Security Initiative, CBP works jointly with host nation counterparts to identify and screen containers that pose a risk at the foreign port of departure before they are loaded on board vessels bound for the U.S. CSI is implemented in 20 of the largest ports in terms of container shipments to the U.S., and at a total of 58 ports worldwide.

The Secure Electronic Network for Travelers Rapid Inspection (SENTRI) program allows pre-screened, low-risk travelers from Mexico to be processed through dedicated lanes. NEXUS is a similar program on the country's northern border with Canada. Along both borders, CBP has implemented the Free and Secure Trade, which uses transponder technology and pre-arrival shipment information to process participating trucks as they arrive at the border. An agreement with Canada allows CBP to target, screen, and examine rail shipments headed to the U.S.

CBP is authorized to provide aerial surveillance outside of the border area "to assist law enforcement and humanitarian relief efforts" when requested by local, tribal, state or federal agencies. CBP drones have been used to capture images of storm-impacted areas for the National Weather Service; assess hurricane affected areas for FEMA; support immigration enforcement actions by ICE; and provide surveillance for local law enforcement during the 2015 Baltimore protests, the 2020 George Floyd protests, and the 2025 Los Angeles protests.

CBP has the authority to search outbound and inbound shipments, and uses targeting to carry out its mission in this area. Under Section 596 of the Tariff Act, CBP is required to seize and forfeit all merchandise that is stolen, smuggled, or clandestinely imported or introduced. CBP is also required to seize and forfeit controlled substances, certain contraband articles, and plastic explosives that do not contain a detection agent. In conjunction with the Department of State and the Bureau of the Census, CBP has put in place regulations that require submission of electronic export information on U.S. Munitions List and for technology for the Commerce Control List. CBP uses advance information from the Automated Targeting System and the Automated Export System to identify cargo that may pose a threat. CBP also works with the departments of state and defense to improve procedures on exported shipments of foreign military sales commodities.