Civil Registration of Ontario births, deaths and marriages began 01 July 1869.

The Archives of Ontario holds records of births from 1869 to 1908, marriages from 1869 to 1923, and deaths from 1869 to 1933. Incomplete marriage registers prior to 1869 are also available.
Ancestry.ca (requires payment) includes indexed and images for: (requires payment) includes indexed and images for:
-Ontario Births 1869-1913
-Ontario Marriages 1857-1926
-Ontario Deaths 1869-1934
-Ontario Civil Marriage Registrations 1869-73
-Ontario Roman Catholic Marriages 1827-1870

Archives of Ontario
The Archives of Ontario holds records of births from 1869 to 1908, marriages from 1869 to 1923, and deaths from 1869 to 1933. Incomplete marriage registers prior to 1869 are also available.

Staff members at the Archives of Ontario office are unable to undertake genealogical searches in these vital records.

Microfilm copies of the indexes and the original registrations are available through inter-institutional loan from the Archives of Ontario and through your local Family History Library.

Registrar General
For births after 1909, marriages after 1926, and deaths after 1934, requests should be addressed to:

Office of the Registrar General
PO Box 4600
189 Red River Road
Thunder Bay ON
P7B 6L8

Information on how to obtain these records is available https://www.orgforms.gov.on.ca/eForms/start.do?lang=en