The South Coast Air Quality Management District says the order begins at midnight and expires 24 hours later.
The agency says a forecast of dense fog, combined with warm daytime temperature Sunday will likely form smog. It says the burn ban would help bring particle pollution levels down to healthy levels.
First-time violators could be fined $50, and repeat offenders could face fines of up to $500.
The AQMD said areas under the ban include downtown and the central San Fernando Valley.
New air pollution rules that limit the use of wood-burning fireplaces in Southern California took effect a year ago.