The Lieutenant Governor of Ontario /lɛfˈtɛnənt/ is the viceregal representative in Ontario of the Canadian monarch, King Charles III, who operates distinctly within the province but is also shared equally with the ten other jurisdictions of Canada, as well as the other Commonwealth realms and any subdivisions thereof, and resides predominantly in his oldest realm, the United Kingdom. The Lieutenant Governor of Ontario is appointed in the same manner as the other provincial viceroys in Canada and is similarly tasked with carrying out most of the monarch's constitutional and ceremonial duties.

Lieutenant Governors of Upper Canada, 1791 to 1841

Lieutenant Governors under King George III (1791 to 1820)

• John Graves Simcoe (1791 to 1796)
  • Peter Russell (Administrator) (1796 to 1799)
• Peter Hunter (1799 to 1805)
• Alexander Grant (11 August 1805 to 24 August 1806)
• Francis Gore (1806 to 1811)
  • Sir Isaac Brock (Acting) (1811 to 13 October 1812)
  • Sir Roger Hale Sheaffe (Acting) (13 October 1812 to 1813)
  • Francis de Rottenburg, baron de Rottenberg (Acting) (1813)
  • Sir Gordon Drummond (Acting) (1813 to 1814)
  • Sir George Murray (Acting) 1815
  • [ Sir Frederick Philipse Robinson, GCB Frederick Philipse Robinson] (Acting) 1815
• Francis Gore (2nd term) (1815 to 1817)
  • Samuel Bois Smith (Administrator) (11 June 1817 to 13 August 1818)
• Sir Peregrine Maitland (13 August 1818 to →)

Lieutenant Governors under King George IV (1820 to 1830)

• cont.... (← to August 1828)
• Sir John Colborne (August 1828 to →)

Lieutenant Governors under King William IV (1830 to 1837)

• cont.... (← to 1836)
• Sir Francis Bond Head (1836 to →)

Lieutenant Governors under Queen Victoria (1837 to 1841)

• cont.... (← to 1838)
• Sir George Arthur (1838 to 1839)
• The Lord Sydenham (1839 to to →)

Lieutenant Governors of Canada West, 1841 to 1867

Lieutenant Governors under Queen Victoria (1841 to 1867)

• cont.... (← to 1841)
• John Clitherow (1841 to 1841)
• Sir Richard Downes Jackson (1841 to 1842)
• Sir Charles Bagot (1842 to 1843)
• Sir Charles Metcalfe (1843 to 1845)
• The Earl Cathcart (26 November 1845 to 30 January 1847)
• The Earl of Elgin and Kincardine (1847 to 1854)
• Sir Edmund Walker Head (1854 to 1861)
• The Vicount Monck (1861 to 30 June 1867)

Lieutenant Governors of Ontario, 1867–present

Lieutenant Governors under Queen Victoria (1867 to 1901)

• Sir Henry William Stisted (1 July 1867 to 14 July 1868)
• Sir William Pearce Howland (15 July 1868 to 11 November 1873)
• John Willoughby Crawford (12 November 1873 to 13 May 1875)
• Donald Alexander Macdonald (18 May 1875 to 30 June 1880)
• John Beverley Robinson (1 July 1880 to 31 May 1887)
• Sir Alexander Campbell (1 June 1887 to 24 May 1892)
• Sir George Airey Kirkpatrick (30 May 1892 to 7 November 1896)
  • [ Sir Casimir Stanislaw Gzowski Kazimierz Stanislaus Gzowski] (Acting) (7 November 1896 to 18 November 1897)
• Sir Oliver Mowat (18 November 1897 to →)

Lieutenant Governors under King Edward VII (1901 to 1910)

• cont.... (← to 19 April 1903)
• Sir William Mortimer Clark (21 April 1903 to 21 September 1908)
• Sir John Morison Gibson (21 September 1908 to →)

Lieutenant Governors under King George V (1910 to 1936)

• cont.... (← to 26 September 1914)
• Sir John Strathearn Hendrie (26 September 1914 to 20 November 1919)
• Lionel Herbert Clarke (20 November 1919 to 29 August 1921)
• Henry Cockshutt (10 September 1921 to 12 January 1927)
• William Donald Ross (12 January 1927 to 25 October 1931)
  • Sir William Mulock (Acting) (25 October 1931 to 1 November 1932)
• Herbert Alexander Bruce (1 November 1932 to →)

Lieutenant Governors under King Edward VIII (1936)

• cont.... (← to →)

Lieutenant Governors under King George VI (1936 to 1952)

• cont.... (← to 23 November 1937)
• Albert Edward Matthews (23 November 1937 to 26 December 1946)
• Ray Lawson (26 December 1946 to →)

Lieutenant Governors under Queen Elizabeth II (1952 to present)

• cont.... (← to 18 February 1952)
• Louis Orville Breithaupt (18 February 1952 to 30 December 1957)
• John Keiller MacKay (30 December 1957 to 1 May 1963)
• William Earl Rowe (1 May 1963 to 4 July 1968)
• William Ross Macdonald (4 July 1968 to 10 April 1974)
• Pauline Mills McGibbon (10 April 1974 to 15 September 1980)
• John Black Aird (15 September 1980 to 20 September 1985)
• Lincoln Alexander (20 September 1985 to 10 December 1991)
• Hal Jackman (11 December 1991 to 24 January 1997)
• Hilary Weston (24 January 1997 to 7 March 2002)
• James Bartleman (7 March 2002 to 5 September 2007)
• David Onley (5 September 2007 to 23 September 2014)
• Elizabeth Dowdeswell (23 September 2014 to →)

Lieutenant Governors under King Charles III (2022 to present)

• cont.... (← to 14 November 2023)
• Edit Dumont (14 November 2023 to present)