Toronto's first mayor, William Lyon Mackenzie, was appointed in 1834 after his Reform coalition won the new City of Toronto's first election and he was chosen by the Reformers. The most recent election to the office of mayor was a by-election on June 26, 2023 in which Olivia Chow was elected. Chow formally took office on July 12, 2023.

If a vacancy occurs, the City of Toronto Act explicitly states that the deputy mayor of Toronto assumes certain limited mayoral powers, but remains deputy mayor during a vacancy. They do not become an acting or interim mayor.

History From 1834 to 1857, and again from 1867 to 1873, Toronto mayors were not elected directly by the public. Instead, after each annual election of aldermen and councilmen, the assembled council would elect one of their members as mayor. For all other years, mayors were directly elected by popular vote, except in rare cases where a mayor was appointed by council to fill an unexpired term of office. Prior to 1834, Toronto municipal leadership was governed by the Chairman of the General Quarter Session of Peace of the Home District Council.

Through 1955 the term of office for the mayor and council was one year; it then varied between two and three years until a four-year term was adopted starting in 2006. (See List of Toronto municipal elections.)

John Tory, who served from 2014 to 2023, resigned as mayor in February 2023; Deputy Mayor Jennifer McKelvie had assumed some mayoral responsibilities as a result until a successor was chosen.

The "City of Toronto" has changed substantially over the years: the city annexed or amalgamated with neighbouring communities or areas 49 times from in 1883 to 1967. The most sweeping change was in 1998, when the six municipalities comprising Metropolitan Toronto—East York, Etobicoke, North York, Scarborough, York, and the former city of Toronto–and its regional government were amalgamated into a single City of Toronto (colloquially dubbed the "megacity") by an act of the provincial government. The newly created position of mayor for the resulting single-tier mega-city replaced all of the mayors of the former Metro municipalities. It also abolished the office of the Metro Chairman, which had formerly been the most senior political figure in the Metro government before amalgamation.

According to Victor Loring Russell, author of Mayors of Toronto Volume I, 14 out of the first 29 mayors were lawyers. According to Mark Maloney who is writing The History of the Mayors of Toronto, 58 of Toronto's 64 mayors (up to Ford) have been Protestant, white, English-speaking, Anglo-Saxon, property-owning males. There have been three women (Hall, Rowlands, and Chow) and three Jewish mayors (Phillips, Givens and Lastman). According to Jewish religious law Tory is also Jewish, because his matrilineal line is Jewish, but he does not consider himself as Jewish.

Art Eggleton is the longest-serving mayor of Toronto, serving from 1980 until 1991. Eggleton later served in federal politics from 1993 until 2004, and was appointed to the Senate of Canada in 2005. David Breakenridge Read held the post of mayor of Toronto for the shortest period; Read was mayor for only fifty days in 1858.

No Toronto mayor has been removed from office. Toronto's 64th mayor, Rob Ford, lost a conflict of interest trial in 2012, and was ordered to vacate his position; but the ruling was stayed pending an appeal, which Ford won to remain in office. Due to his substance abuse admission and controversy in 2013, Council stripped him of many powers on November 15, transferring them to the deputy mayor. From May until July, 2014, Ford took a leave of absence from the mayoralty to enter drug rehabilitation.

Original City of Toronto era

+ Appointed by City Council No. Mayor Took office Left office Prior political experience 1 William Lyon Mackenzie 1834 (March 27) 1835 Member of the Upper Canada Legislative Assembly for York(1829–1834, expelled several times)Alderman for St. David's Ward (1834) 2 Robert Baldwin Sullivan 1835 (January 15) 1836 Alderman for St. David's Ward (1835) 3 Thomas David Morrison 1836 1837 Member of the Legislative Assembly of Upper Canada for 3rd York (1835–1840)Alderman for St Andrew's Ward (1834–1836) 4 George Gurnett 1837 1838 Alderman for St. George's Ward (1834–1850) 5 John Powell 1838 1841 Alderman for St. Andrew's Ward (1837–1841) 6 George Monro 1841 1842 Alderman for St. Lawrence’s Ward (1834–1835, 1837–1845) 7 Henry Sherwood 1842 1845 Member of the Legislative Assembly of Upper Canada for Brockville (1836–1840)Alderman for St. David's Ward (1842–1849)Member of the Legislative Assembly of the Province of Canada for Toronto (1843–1851) 8 William H. Boulton 1845 1848 Alderman for St. Patrick's Ward (1838–1843, 1844–1852)Mayor (1845–1847)Member of the Legislative Assembly of the Province of Canada for Toronto (1844–1853) – George Gurnett(2nd incumbency) 1848 1851 Alderman for St. George's Ward (1834–1850) 9 John George Bowes 1851 1854 Alderman for St. James's Ward (1850–1853) 10 Joshua George Beard 1854 1855 Alderman for St. Lawrence Ward (1834–1854)Toronto School Board of Trustees (1850–1864) 11 George William Allan 1855 1856 Alderman for St. David Ward (1849–1855) 12 John Beverley Robinson 1856 1857 Alderman for St. Patrick's Ward (1851, 1853–54, 1856–57) 13 John Hutchison 1857 1858 (resigned) Alderman for St. James Ward (1852–1853, 1856–1857) – William H. Boulton(2nd incumbency) 1858 1858 (resigned November 8) Alderman for St. Patrick's Ward (1838–1843, 1844–1852)Mayor (1845–1847)Member of the Legislative Assembly of the Province of Canada for Toronto (1844–1853)Alderman for St. Andrew's Ward (1858) 14 David Breakenridge Read 1858 (November 11) 1858 (December 31) Alderman for St. Patrick's Ward (1858)

+ Elected directly by the public No. Mayor Took office Left office Prior political experience 15 (Sir) Adam Wilson 1859 1861 Alderman for St. Patrick's Ward (1855) – John George Bowes(2nd incumbency) 1861 1864Alderman for St. James's Ward (1850) Alderman for St. James's Ward and Mayor (1851–1853) Alderman for St. David's Ward (1856) 16 Francis Henry Medcalf 1864 1867Alderman for St. Lawrence Ward (1860)Alderman for St. David's Ward (1863)

+ Appointed by City Council No. Mayor Took office Left office Prior political experience 17 James Edward Smith 1867 1869 Alderman for St. John's Ward (1857–1867) 18 Samuel Bickerton Harman 1869 1871 Alderman for St Andrew's Ward (1866–1868, 1871–1872) 19 Joseph Sheard 1871 1873 Alderman for St. Patrick's Ward (1851–1871) 20 Alexander Manning 1873 1874 Alderman for St. Lawrence Ward (1856–1858, 1867–1873)

+ Elected directly by the public No. Mayor Took office Left office Prior political experience – Francis Henry Medcalf (2nd incumbency) 1874 1875Alderman for St. Lawrence Ward (1860)Alderman for St. David's Ward (1863, 1867–1868)Mayor (1864–1867) 21 Angus Morrison 1876 1878Alderman for St. James (1853–1854)Member of the Legislative Assembly of the Province of Canada for North Simcoe (1854–1863) and Niagara (1864–1867) Member of Parliament (1867–1874) 22 James Beaty 1879 1880Alderman for St. James's Ward (1877) 23 William Barclay McMurrich 1881 1882Alderman for St. Patrick's Ward (1879–1880) 24 Arthur Radcliffe Boswell 1883 1884 Alderman for St. George's Ward (1877–1879, 1882) – Alexander Manning (2nd incumbency) 1885 1885 Alderman for St. Lawrence Ward (1856–1858, 1867–1873)Mayor (1873) 25 William Holmes Howland 1886 1887President of the Toronto Board of Trade (1874–75)President of the Dominion Board of Trade (1874)President of the Manufacturers’ Association of Ontario (1877–78) 26 Edward Frederick Clarke 1888 1891Member of the Legislative Assembly for Toronto (1886–1894) 27 Robert John Fleming 1892 1893Alderman for St. David's Ward (1886–1890) 28 Warring Kennedy 1894 1895Alderman for St. John's Ward (1871) – Robert John Fleming(2nd incumbency) 1896 1897 (resigned August 5) Alderman for St. David's Ward (1886–1890)Mayor (1892) 29 John Shaw 1897 (August 6) 1899 Alderman for St. Paul's Ward (1883–1895)Alderman for Ward 3 (1897)"Mayor Fleming's Fourth Triumph", The Globe (1844-1936); Toronto, Ont. [Toronto, Ont]05 Jan 1897: 2 30 Ernest A. Macdonald 1900 1900Alderman for St. Matthew's Ward (1886–1887, 1889–1890)Alderman for Ward 1 (1896)"IT IS FLEMING: The People's "Bob" Overwhelms Ald. Shaw A DECISIVE MAJORITY The Council of 1895 Was Decidedly Popular RETIRING ALDERMEN ELECTED F. S. Spence and W. T. R. Preston Gain a Footing Mr. Spence Heads the Poll for a Start--The Aldermen and the Aqueduct Question", The Globe (1844-1936); Toronto, Ont. [Toronto, Ont]07 Jan 1896: 6. 31 Oliver Aiken Howland 1901 1902Member of the Legislative Assembly for Toronto South (1894–1898) 32 Thomas Urquhart 1903 1905Alderman for Ward 4 (1900–1902) 33 Emerson Coatsworth 1906 1907 Member of Parliament for Toronto East (1891–1896)Alderman for Ward 2 (1904–1905)"Thomas Urquhart Gets Third Term", The Globe (1844-1936); Toronto, Ont. [Toronto, Ont]03 Jan 1905: 1, 8 34 Joseph Oliver 1908 1909 Toronto School Board Trustee (1885)Alderman for Ward 2 (1895, 1901–1903 (also Board of Control) and 1906)FLEMING'S JUBILATION: The Mayor Addresses a Large Gathering ENTHUSIASM ON THE STREET The Crowd Rejoices at the Election The Result Regarded as a Triumph for Honest Mothods at the City Hall AN AMAZING VICTORY HIS LAST TERM GRATEFUL TO THE WOMEN WORDS OF CONGRATULATION Full TextHistorical Newspapers, The Globe (1844-1936); Toronto, Ont. [Toronto, Ont]05 Jan 1897: 3HOWLAND IS MAYOR: HisPluralityOver Spence Fully Four Thousand SHAW NOWHERE The Desertion From His Ranks Was Complete SEVEN NEW ALDERMEN Old Members Slaughtered In the Third. Fifth and Sixth WardsMunicipal Gas Plant Favored The Globe (1844-1936); Toronto, Ont. [Toronto, Ont]08 Jan 1901: 1"COATSWORTH AND LIQUOR; NESBITT MACHINE WINS: Majorities Against Spence and the Reduction By-laws FIGURES THAT SIGNIFY MUCH Coatsworth's Majorities Greatest in Strongholds of Liquor Men Controller Spence the Only Member of a Civic Board to Fail of Re-election Two Ex-Members and One New Aspirant Elected to the Council Aid. Jones Becomes a Member of the Board of Control No Change in the Board of Education-- Majorities Against the Reduction By-laws Large Controller Spence Attributes His Defeat to Effective Organization Formed For Defeat of Liquor License By-laws-- Coatsworth Calls it Victory of People", The Globe (1844-1936); Toronto, Ont. [Toronto, Ont]02 Jan 1906: 1 35 George Reginald Geary 1910 1912 (resigned October 21)Toronto School Board Trustee (1904)Alderman for Ward 3 (1905–1908)Toronto Board of Control (1909) 36 Horatio C. Hocken 1912 1914Toronto Board of Control (1907–1909, 1911–1912) 37 Thomas Langton Church 1915 1921Toronto School Board Trustee (1899–1904)Alderman for Ward 2 (1905–1909)Toronto Board of Control (1910–1914) 38 Charles A. Maguire 1922 1923Alderman for Ward 3 (1909–1912, 1914–1917)Toronto Board of Control (1918–1921) 39 W. W. Hiltz 1924 1924Toronto School Board Trustee (1911–1913)