It will go into effect starting Aug. 1.
This declaration allows the mayor and other city officials to marshal resources and personnel to confront the outbreak.
RELATED: Everything you need to know about monkeypox origin, infection, vaccines, and treatment
"If there were any other community that was disproportionately impacted by monkeypox the way the gay community has been impacted, this whole country would be up in arms," said San Francisco Mayor London Breed.
Mayor Breed held an impassioned news conference inside city hall Thursday.
"By sounding the alarm, what we're saying is this is not going to be ignored. That this is a public health crisis," Breed said.
According to the San Francisco Department of Public Health, the city currently has 281 cases - with a disproportionate number among men who have sex with men.
That number has grown exponentially over the past few weeks.
RELATED: Santa Clara Co. outlines monkeypox strategy, shares data on who's disproportionately impacted
"I have talked to too many doctors and too many folks who have gotten monkeypox, who have described the symptoms that are associated with this. The potentially lifelong disfigurement that can come from monkeypox. People need to take this seriously," said Supervisor Rafael Mandelman.
For weeks, demand for the monkeypox vaccine has far outstripped supply.
People have been lining up for hours only to be told none were available.
As of Thursday, San Francisco has received around 12,000 doses. But health officials say about 70,000 are actually needed.
"It's wild to look back and think, did we learn nothing? We just went through a pandemic where everyone was like, 'oh my god if a vaccine was available to everyone, we would be in such a better space.' And now, this thing is happening, this crisis is happening," said Clayton Bishop.
RELATED: Report: US government took 'wait-and-see' monkeypox approach; deprioritized gay men's health
Bishop got a vaccine a few weeks ago by luck.
He wishes the federal government's response to monkeypox outbreak would have been better.
It's a view shared by many in the LGBTQ+ community.
"This is an infuriating moment for our community that is being caused harm by the lack of urgency in this moment of crisis," said Tyler TerMeer of the San Francisco AIDS Foundation.
RELATED: California lawmakers pressure federal officials to boost monkeypox vaccine production
So while leaders rush to avoid a catastrophe, LGBTQ+ advocate groups say they're here for the community.
Being a source of comfort and information during increasingly uncertain times.
"Each and every day at San Francisco AIDS Foundation, we have hundreds of people calling our monkeypox hotline with questions and concerns, fear and anxiety," TerMeer said.
There are reportedly 799 cases in California, over 4,600 cases in the United States, and more than 19,000 cases globally.