The mayor of the City and County of San Francisco is the head of the executive branch of the San Francisco city and county government. The officeholder has the duty to enforce city laws, and the power to either approve or veto bills passed by the San Francisco Board of Supervisors, the legislative branch. The mayor serves a four-year term and is limited to two successive terms. Because of San Francisco's status as a consolidated city-county, the mayor also serves as the head of government of the county; both entities have been governed together by a combined set of governing bodies since 1856.

There have been 45 individuals who have served as mayor in San Francisco since 1850, when California became a state following the American Conquest of California. Prior to the conquest, Californios served as Mayor of San Francisco during the Spanish and Mexican eras since 1779.

The current mayor is former District 5 supervisor and president of the Board of Supervisors London Breed, who won a special election following the death of Mayor Ed Lee on December 12, 2017. Breed served out the remainder of Lee's uncompleted term (until January 8, 2020), after which she is eligible to run for two full terms of her own including the 2019 San Francisco mayoral election which she won.

The mayor of San Francisco is elected every four years; until 2019 elections took place one year before United States presidential elections on election day in November. Candidates must live and be registered to vote in San Francisco at the time of the election. The mayor is usually sworn in on the January 8 following the election.

The next election for a full mayoral term will be in 2024. In 2022, San Francisco voters passed Proposition H, which changed mayoral elections to the same cycle as presidential elections. This gives London Breed an additional year to her first full term. This change was proposed because of the low turnout in off-year elections. For example, 2019 saw a turnout of only 42%, while 2020 saw 86% turnout.

Under the California constitution, all city elections in the state are conducted on a non-partisan basis. As a result, candidates' party affiliations are not listed on the ballot, and multiple candidates from a single party can run in the election.

Mayoral elections were originally run under a two-round system. If no candidate received a simple majority of votes in the general election, the two candidates who received the most votes competed in a second runoff election held several weeks later. In 2002, the election system for city officials was overhauled as a result of a citywide referendum. The new system, known as instant-runoff voting, allows voters to select and rank three candidates based on their preferences. If no one wins more than half of the first-choice votes, the candidate with the fewest votes is eliminated and second-choice votes (and third-choice votes, if necessary) are counted until a candidate captures the majority. This eliminates the need to hold a separate runoff election and saves money. This was first implemented in the 2004 Board of Supervisors election after two years of preparation. In 2007, the new system was implemented in the mayoral election for the first time.

As of 2017, the mayor is paid an annual salary of $342,974, the highest mayoral salary in the United States. Nine city public employees earned higher salaries than the mayor, including the chief investment officer and the managing director of the San Francisco Employees' Retirement System, who oversee the city's pension plan.

Unlike a few other American cities, the San Francisco mayor does not have an official residence; in the 1990s, Mayor Willie Brown unsuccessfully pushed to acquire the Yerba Buena Island mansion formerly used by U.S. Navy admirals as a ceremonial residence for the mayor.

The mayor has the responsibility to enforce all city laws, administer and coordinate city departments and intergovernmental activities, set forth policies and agendas to the Board of Supervisors, and prepare and submit the city budget at the end of each fiscal year. The mayor has the powers to either approve or veto bills passed by the San Francisco Board of Supervisors, participate in meetings of the Board of Supervisors and its committees, appoint a replacement to fill vacancies in all city elected offices until elections, appoint a member of the Board to serve as acting mayor in the absence of the mayor, and to direct personnel in the case of emergency.

When mayors die in office, resign, or are unable to carry out their duties, and did not designate an acting mayor, the president of the Board of Supervisors becomes acting mayor until the full Board selects a person to fill the vacancy and finish the previous mayoral term. (In the case that both the president of the Board of Supervisors and the mayor are incapacitated, the order of succession is followed.) This has happened seven times: James Otis died in office and was succeeded by George Hewston, Eugene Schmitz was removed and succeeded by Charles Boxton, Charles Boxton resigned and was succeeded by Edward Robeson Taylor, James Rolph resigned and was succeeded by Angelo Rossi, George Moscone was assassinated and was succeeded by Dianne Feinstein, Gavin Newsom resigned and was succeeded by Ed Lee, and Lee died in office and was succeeded by London Breed before the San Francisco Board of Supervisors selected Mark Farrell as interim mayor.

To date, 44 individuals have served as San Francisco mayor. There have been 45 mayoralties due to Charles James Brenham's serving two non-consecutive terms: he is counted chronologically as both the second and fourth mayor. The longest term was that of James Rolph, who served over 18 years until his resignation to become the California governor. The length of his tenure as mayor was largely due to his popularity. During his term, San Francisco saw the expansion of its transit system, the construction of the Civic Center and the hosting of the World's Fair. The shortest term was that of Charles Boxton, who served only eight days before resigning from office. Three mayors have died in office: Otis died from illness, Moscone was assassinated in 1978, and Lee died from cardiac arrest. Dianne Feinstein and London Breed are the only women who have served as mayor, both of them by succession and by election; Willie Brown and London Breed are the only African Americans to serve to date; Ed Lee is the only Asian American to serve as mayor. Three mayors have Jewish ancestry: Washington Bartlett (Sephardi), Adolph Sutro (Ashkenazi), and Dianne Feinstein (Ashkenazi). Thirteen mayors are native San Franciscans: Levi Richard Ellert, James D. Phelan, Eugene Schmitz, James Rolph, Elmer Robinson, John F. Shelley, Joseph Alioto, George Moscone, Dianne Feinstein, Frank Jordan, Gavin Newsom, Mark Farrell, and London Breed. Four mayors are foreign-born: Frank McCoppin and P.H. McCarthy (United Kingdom of Great Britain and Ireland, both born in what is now the Republic of Ireland), Adolph Sutro (Prussia, part of Germany since 1871) and George Christopher (Greece).

This list does not include acting mayors who are typically appointed whenever the mayor will be out of the city.

#	Image	Mayor	Term start	Term end	Party
1		John W. Geary	May 1, 1850	May 4, 1851		Independent
2		Charles James Brenham	May 5, 1851	December 31, 1851		Whig
3		Stephen Randall Harris	January 1, 1852	November 9, 1852		Democratic
4		Charles James Brenham	November 10, 1852	October 2, 1853		Whig
5		Cornelius Kingsland Garrison	October 3, 1853	October 1, 1854		Whig
6		Stephen Palfrey Webb	October 2, 1854	June 30, 1855		Know Nothing
7		James Van Ness	July 1, 1855	July 7, 1856		Democratic
8		George J. Whelan	July 8, 1856	November 14, 1856		American
9		Ephraim Willard Burr	November 15, 1856	October 2, 1859		American
10		Henry F. Teschemacher	October 3, 1859	June 30, 1863		Populist
11		Henry Perrin Coon	July 1, 1863	December 1, 1867		Populist
12		Frank McCoppin	December 2, 1867	December 5, 1869		Democratic
13		Thomas Henry Selby	December 6, 1869	December 3, 1871		Republican
14		William Alvord	December 4, 1871	November 30, 1873		Republican
15		James Otis	December 1, 1873	October 30, 1875		Populist
16		George Hewston	November 4, 1875	December 5, 1875		Democratic
17		Andrew Jackson Bryant	December 6, 1875	November 30, 1879		Populist
18		Isaac Smith Kalloch	December 1, 1879	December 4, 1881		Workingmen's
19		Maurice Carey Blake	December 5, 1881	January 7, 1883		Republican
20		Washington Bartlett	January 8, 1883	January 2, 1887		Democratic
21		Edward B. Pond	January 3, 1887	January 4, 1891		Democratic
22		George Henry Sanderson	January 5, 1891	January 3, 1893		Republican
23		Levi Richard Ellert	January 3, 1893	January 6, 1895		Republican
24		Adolph Sutro	January 7, 1895	January 3, 1897		Populist
25		James D. Phelan	January 4, 1897	January 7, 1902		Democratic
26		Eugene Schmitz	January 8, 1902	July 8, 1907		Union Labor
27		Charles Boxton	July 9, 1907	July 16, 1907		Union Labor
28		Edward Robeson Taylor	July 16, 1907	January 7, 1910		Democratic
29		P. H. McCarthy	January 8, 1910	January 7, 1912		Union Labor
30		James Rolph	January 8, 1912	January 6, 1931		Republican
31		Angelo Joseph Rossi	January 7, 1931	January 7, 1944		Republican
32		Roger Lapham	January 8, 1944	January 7, 1948		Republican
33		Elmer Robinson	January 8, 1948	January 7, 1956		Republican
34		George Christopher	January 8, 1956	January 7, 1964		Republican
35		John F. Shelley	January 8, 1964	January 7, 1968		Democratic
36		Joseph Alioto	January 8, 1968	January 7, 1976		Democratic
37		George Moscone	January 8, 1976	November 27, 1978		Democratic
38		Dianne Feinstein	December 4, 1978	January 7, 1988		Democratic
39		Art Agnos	January 8, 1988	January 7, 1992		Democratic
40		Frank Jordan	January 8, 1992	January 7, 1996		Democratic
41		Willie Brown	January 8, 1996	January 7, 2004		Democratic
42		Gavin Newsom	January 8, 2004	January 10, 2011		Democratic
43		Ed Lee	January 11, 2011	December 12, 2017		Democratic
44		Mark Farrell	January 23, 2018	July 11, 2018		Democratic
45		London Breed	July 11, 2018	Incumbent		Democratic

#	Image	Mayor	Term start	Term end	Party
46		Daniel Lurie	January 6, 2025	Incoming		Democratic

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