Breed said the order will go into effect at midnight and will remain until April 7.
Necessary government functions and essential stores will remain open.
In a news conference, Breed urged residents to not panic and to not rush out to stores.
She said there is no need to rush out to gather supplies since places like grocery stores, gas stations, convenience stores and banks will remain open.
“It’s the new normal temporarily to protect public health,” San Francisco Mayor London Breed said at a news conference. “These measures will be disruptive to day to day life, but there is no need to panic.”
People should work from home unless they provide essential services, such as public safety, sanitation and medical services. Pharmacies and banks will remain open. Restaurants will be open only for take-out, Breed said.
The dramatic step came as officials across California took increasingly strident steps to separate people and contain the spread of coronavirus, prompting millions of the state’s oldest and youngest residents to stay home Monday.
San Francisco joins five other Bay Area counties issuing this order. The other counties are Marin, Santa Clara, San Mateo, Alameda and Contra Costa.
San Francisco reported three new cases Monday, bringing the total number of coronavirus cases in the city to 40.