The National Automobile, Aerospace, Transportation and General Workers Union of Canada, commonly known as the Canadian Auto Workers (CAW), was one of Canada's largest labour unions. In 2013, it merged with the Communications, Energy and Paperworkers Union of Canada, forming a new union, Unifor. While rooted in Ontario's large auto plants of Windsor, Brampton, Oakville, St. Catharines, and Oshawa, the CAW has expanded and now incorporates workers in almost every sector of the economy. The presidents of the CAW were Bob White (1985–1992), Buzz Hargrove (1992–2008), Ken Lewenza (2008–2013), and Jerry Dias (2013–2022) when the CAW became UNIFOR.

The United Auto Workers (UAW), fully named International Union, United Automobile, Aerospace and Agricultural Implement Workers of America, is an American labor union that represents workers in the United States and southern Ontario, Canada. It was founded as part of the Congress of Industrial Organizations (CIO) in the 1930s and grew rapidly from 1936 to the 1950s. The union played a major role in the liberal wing of the Democratic Party under the leadership of Walter Reuther. It was known for gaining high wages and pensions for automotive manufacturing workers, but it was unable to unionize auto plants built by foreign-based car makers in the South after the 1970s, and it went into a steady decline in membership; reasons for this included increased automation, decreased use of labor, mismanagement, movements of manufacturing, and increased globalization. After a successful strike at the Big Three in 2023, the union organized its first foreign plant (VW) in 2024.