Section 21 of the Constitution Act, 1867

Proclamation bringing the Constitution Act into force, July 1, 1867

Section 21 of the Constitution Act, 1867 (French: article 21 de la Loi constitutionnelle de 1867) is a provision of the Constitution of Canada relating to the composition of the Senate of Canada. The section sets out the total number of senators, currently set at 105. Section 21 originally provided that the Senate would be composed of 72 senators, but that number has gradually increased as new provinces and territories joined Confederation.

The Constitution Act, 1867 is the constitutional statute which established Canada. Originally named the British North America Act, 1867, the Act continues to be the foundational statute for the Constitution of Canada, although it has been amended many times since 1867. It is now recognised as part of the supreme law of Canada.