The Chair of the Los Angeles County also called Chair of the Los Angeles County Board of Supervisors is responsible for the day-to-day operations of the county government. The chair is the presiding officer for the Los Angeles County Board of Supervisors.^[1] The board members serve as chair for one year each on a rotating basis. One chair, Michael D. Antonovich, called himself the Mayor of Los Angeles County.

The Chair of the Board of Supervisors serves a term of one year. Upon expiration of the term the duties of the Chair are rotated among the board members by order of seniority until 2015 when the board unanimously move the rotation by order of district. When Chair Pro Tem Sheila Kuehl announced her retirement at the end for her supervisorial term her term would expire before her Chair term would begin Janice Hahn was selected to be Chair and Lindsey Horvath was Chair Pro Tem allowing Horvath to become Chair the following year and Kathryn Barger was selected to be Chair Pro Tem to resume district rotation of the County Chair. The term for a supervisor typically lasts four years, any member will get to serve as chair at least once during the duration of their term. The chair may be stylized as "mayor", a practice that was started and only observed by Michael D. Antonovich during his tenure as a supervisor. This tradition was not continued by the current incumbents.^[2][1][3]

These are the chairs/mayors of the Los Angeles County Board of Supervisors:^[5][6][7]

"The Mayor/Chair shall possess the powers and perform the duties prescribed, as follows:

a. Have general direction over the Board Room and assign seats for the use of the members;

b. Preserve order and decorum; prevent demonstrations; order removed from the Board Room any person whose conduct deemed objectionable; and order the Board Room cleared whenever deemed necessary (Government Code Section 54957.9, see Appendix);

c. Assure that attendants of the public at meetings in the Board Room shall be limited to that number which can be accommodated by the seating facilities regularly maintained therein. No standees shall be permitted;

d. Allocate the length of time for public discussion of any matter in advance of such discussion, with the concurrence of the Board;

e. Allocate equal time to opposing sides insofar as possible taking into account the number of persons requesting to be heard on any side;

f. Limit the amount of time that a person may address the Board during a public discussion period in order to accommodate those persons desiring to speak and to facilitate the business of the Board;

g. Authorize not more than one Set Matter per Board meeting. Any additional Set Matters shall require Board action; and

h. Instruct a member of the public who wishes to address the Board on a matter under the supervision of the Department of Children and Family Services that such matter is not within the subject matter jurisdiction of the Board, that it is not within the power of the Board to alter the outcome of a court matter, and that case identifying information is confidential and may not be disclosed in public; bar public disclosure of such information; and direct the person to Section 38 which outlines the alternate procedure to be followed."^[1]

This section may need to be rewritten to comply with Wikipedia's quality standards. (May 2023)

"At noon on the first Monday in December, in the even-numbered years, the Chair Pro Tem shall automatically succeed to the position of Chair to serve until the election or succession of his/her successor; in the event there is no Chair Pro Tem, the Board shall elect a Mayor/Chair to serve for the said period. If the term of the Mayor/Chair expires in an odd-numbered year, the succession or election as provided herein of the new Mayor/Chair shall take place at 9:30 a.m. the first Tuesday following the first Monday in December. Upon the succession of the Chair Pro Tem to the position of Mayor/Chair."^[1]