The Canada Border Services Agency (CBSA; French: Agence des services frontaliers du Canada, ASFC) is a federal law enforcement agency that is responsible for border control (i.e. protection and surveillance), immigration enforcement, and customs services in Canada.

Established in 2003 by an order-in-council that amalgamated the customs function of the now-defunct Canada Customs and Revenue Agency, the enforcement function of Citizenship and Immigration Canada (now known as Immigration, Refugees and Citizenship Canada), and the port-of-entry examination function of the Canadian Food Inspection Agency (CFIA). The CBSA's creation was formalized by the Canada Border Services Agency Act, which received Royal assent on 3 November 2005. The CBSA is overseen by Parliament through the Minister of Public Safety and Emergency Preparedness.

The CBSA oversees approximately 1,200 service locations across Canada and 35 in other countries. It employs over 16,500 public servants and offers 24-hour service at 117 of its land border crossings and 10 of the 13 international airports it serves. It works closely with Immigration, Refugees and Citizenship Canada to enforce immigration laws by facilitating the removal of inadmissible individuals from the country and assisting local police in the investigation of violations of the Immigration and Refugee Protection Act.

The agency oversees operations at three major sea ports and three CBSA mail centres (CMC), and operates detention facilities, known as immigration holding centres (IHC), in Laval, Quebec; Toronto, Ontario; and Surrey, British Columbia.

CBSA's Inland Enforcement branch tracks down and removes foreign nationals who are in Canada illegally.

Before 2004, border security in Canada was handled by three legacy agencies that performed individual functions:

The auditor general identified the issues in having the responsibility of border security be divided, such as the inability of individual agencies to share certain security information, as well as ineffective inter-agency communication. Thus, in 2003, the border enforcement functions taken on by the separate agencies would consolidate into a singular organization, titled the Canada Border Services Agency, with Alain Jolicoeur appointed as its inaugural president. Originally, under CCRA, Canada Customs was joined with the country's revenue service, though the agency would primarily give its focus to tax collection. With the establishment of Border Services, CCRA's taxation responsibilities would break off into the Canada Revenue Agency, while its customs function would be absorbed entirely by the CBSA.

The agency has since undergone significant changes to its overall structure, as well as to its range of duties and institutional priorities.