From 1763-1947 any person born in Britain or in a British colony was considered a British subject. That included Canada, England, Wales, Scotland, Ireland, Australia, India and the British West Indies.
British subjects were not required to be naturalized if they moved to or from British lands. Immigrants from other countries could apply for citizenship after living in Canada for 2-5 years.
After 1 Jan 1947 any person who wished to live in Canada, but was not born in Canada or born to a Canadian parent, was required to apply for citizenship.
1828-1850: Naturalization Records for Upper Canada / Canada West (Ontario) at Library & Archives Canada
1854-1917: Citizenship & Naturalization Records at Citizenship & Immigration Canada. The original records were destroyed but an index still exists. Only Canadian residents can request this information.
1851-1945: Citizenship Registration Records, Montreal Circuit Court at Library & Archives Canada. Most of the records date between 1868-1916.
1915-1951: Naturalization Lists at Library & Archives Canada. Lists of naturalized persons published by the government, not applications or naturalization records.
1947-: Citizenship Records at Citizenship & Immigration Canada. Only Canadian residents can request this information, and only for someone who died at least 20 years ago. Researchers outside Canada can ask or hire a Canadian resident to apply on their behalf.
Citizenship: To be a citizen of a country. Citizenship is sought by those wishing to live permanently in a country they weren't born in.
Naturalization: When a person is granted full citizenship of a country they weren't born in.