Global Affairs Canada (GAC; French: Affaires mondiales Canada; AMC) is the department of the Government of Canada that manages Canada's diplomatic and consular relations, promotes Canadian international trade, and leads Canada's international development and humanitarian assistance. It is also responsible for maintaining Canadian government offices abroad with diplomatic and consular status on behalf of all government departments.

According to the OECD, Canada's total official development assistance (ODA) (US$7.8 billion, preliminary data) increased in 2022 due to exceptional support to Ukraine and its pandemic response in developing countries, increased costs for in-donor refugees as well as higher contributions to international organizations, representing 0.37% of gross national income (GNI).

The department has undergone numerous name changes and re-organizations since its founding in 1909. Originally established as the "Department of External Affairs", GAC has been known by a variety of names throughout its lifetime. Its current legal name is the Department of Foreign Affairs, Trade and Development, but its "applied" name used within government is Global Affairs Canada often shorted in the Canadian media to simply "Global Affairs".

GAC was first founded as the Department of External Affairs on 1 June 1909.

During and after World War I, Canada assumed greater control over its foreign relations, with its full autonomy in this field confirmed by the Statute of Westminster in 1931. For historical reasons, the name External Affairs was retained.

The Department of Trade and Commerce, which included the Trade Commissioner Service, had been created in 1892. In 1969, it was combined with the Department of Industry to form the Department of Industry Trade and Commerce (ITC). Both External Affairs and ITC maintained networks of offices abroad, with varying degrees of coordination among them. The Department of Citizenship and Immigration also had offices abroad, in some cases dating back to Confederation.

In the 1970s and early 1980s, there were growing efforts to ensure coordination among all Canadian government offices outside Canada and to strengthen the leadership role and authority of heads of post (ambassadors, high commissioners, and consuls general) over all Canadian government staff in their areas of accreditation. This led to a 1979 decision by Prime Minister Joe Clark to consolidate the various streams of the Canadian Foreign Service, including the "political" (traditional diplomatic) stream, the Trade Commissioner Service, and the Immigration Foreign Service.

This was followed in 1982 by Prime Minister Pierre Trudeau's decision to combine External Affairs and International Trade into a single department. It initially retained the name of Department of External Affairs, but was subsequently renamed External Affairs and International Trade. The change was reflected in a new Department of External Affairs Act passed in 1983. The 1982 merger was part of larger reorganization of government that also combined the Industry component of ITC with the Department of Regional Economic Expansion.