Many federal census records are found at the Family History Library, the National Archives of Canada, and at other provincial and local archives. The Canada Census section of the Canada Research Outline provides more detailed information about the federal records.
The Family History Library has Canadian federal censuses of Ontario for 1871, 1881, 1891, and 1901. The 1881 census has been indexed, transcribed and placed online at www.FamilySearch.org.
Index, 1871 Census of Ontario. Most Canadian national censuses are not indexed by province. The Canadian government did not make indexes. The Ontario Genealogical Society prepared an index for the 1871 census of the province:
Elliott, Bruce S., ed. Index to the 1871 Census of Ontario. 30 Volumes. Toronto, Ontario: Ontario Genealogical Society, 1986-1992. (FHL book 971.3 X22i 1871; not on microfilm.) A computer version of the original databases for this index is available at the National Archives of Canada and the Automated Resource Center of the Family History Library. This is listed in the Family History Library Catalog under the heading ONTARIO - CENSUS - 1871 - INDEXES.
The 1871 Ontario census is indexed and online at: http://www.collectionscanada.ca/02/020108_e.html
Pre-1842. The pre-1842 censuses of Ontario were taken each year by local tax assessors and filed with the District Clerk of the Peace. Most have been lost. Those for Augusta Township, Grenville County, are on FHL film 393998. They cover the years 1796, 1806, 1813, 1823, and 1824. Other head-of-household lists made by tax assessors date from the late 1820s and 1830s for some townships. See the "Taxation" section of this outline.
1842-1850. The first census for all of Upper Canada (present southern Ontario) was a head-of-household census taken in 1842. Much of it does not survive. The 1848 and 1850 head-of-household censuses exist for only three of twenty districts then in the province: Huron, Johnstown, and Newcastle. The available 1848 and 1850 censuses are indexed in:
Dilts, Bryan Lee. 1848 and 1850 Canada West (Ontario) Census Index. Salt Lake City, Utah: Index Publishing, 1984. (FHL book 971.3 X22d; not on microfilm.)
1851-61. Important every-name censuses were taken in southern Ontario for 1851 (actually taken in 1852) and 1861. Some sections of these censuses are lost. A list of townships for which these and other censuses are available is in the Ontario section of:
Hillman, Thomas A. Catalogue of Census Returns on Microfilm, 1666-1891. [Ottawa]: National Archives of Canada, 1987. (FHL book 971 X23ht; not on microfilm.)
Census Indexes. A bibliography of available census indexes by township is:
Crowder, Norman K. Indexes to Ontario Census Records: Interim Update. Nepean, Ontario: Crowder, 1992. (FHL book 971.3 X23c 1992; fiche 6075927.)
All census records for Ontario are listed in the Locality Search of the Family History Library Catalog under the headings:
ONTARIO - CENSUS - [YEAR]
ONTARIO, [DISTRICT] - CENSUS - [YEAR]
ONTARIO, [COUNTY] - CENSUS - [YEAR]
ONTARIO, [COUNTY], [TOWN] - CENSUS - [YEAR]
www.ancestry.com has indexed, digitized and placed online most Canadian censuses. This is a subscription website.