The emergency shelter, which will have an initial capacity of 400 and be solely for men, will be housed on an old railway site in the north of the French capital, Hidalgo said.
Asylum-seekers will be allowed to stay there for “five to 10 days” and receive medical care while waiting for a place in a refugee hostel, the Socialist mayor told reporters.
France has not been on the frontline of the vast influx of migrants to Europe in the last 18 months, with many refugees seeing it mainly as a transit country to other destinations in northern Europe.
But it has an acute shortage of accommodation for asylum seekers, with leaving many people to fend for themselves.
Hidalgo said a second centre, for women and children only, will be opened in Ivry-sur-Seine to the southeast of Paris by the end of the year, she added.
The 6.5-million-euro ($7.2 million) Paris shelter will open in an area where hundreds of migrants have been sleeping rough, on the pavement or under railway bridges. By the end of 2016 it will have 600 beds.
The camp will be located not far from Paris’s Gare du Nord train station, which is the main terminal for Eurostar trains to London. The women’s shelter will have 350 places.
Hidalgo, who had announced in May that she would set up a camp in Paris, called it a “first for Europe” and said it was France’s duty to accommodate migrants in “humane” conditions.
‘Change of tack’
Hostility towards migrants, particularly Muslim migrants, has been growing in France in recent months.
A new reception centre in the Essonne area south of Paris was torched on Monday night, investigators said. The centre for Sudanese and Afghan men had been due to open in October.
Many of those in Paris are bound for the port of Calais on the Channel coast, where they hope to stow away on a truck crossing to Britain.
On Monday, dozens of truckers and farmers blocked the main routes in and out of the busy port to call for the closure of the town’s sprawling “Jungle” migrant camp.
Interior Minister Bernard Cazeneuve promised during a visit to the Jungle last week to close the camp down “as quickly as possible” but said it would be done in stages.
Hidalgo has been critical of the government’s approach to the refugee issue, accusing the state of not giving people fleeing war and misery “a fitting welcome”.
As she was speaking Tuesday, police were clearing a makeshift camp set up in the middle of a busy avenue in northeast Paris, where hundreds of migrants had been sleeping rough.
“I’m alone here, I have no family, I don’t know where they’re taking us,” Asam, a 21-year-old Sudanese refugee who stood watching the police with a mattress under his arm, told AFP.
Since June 2015, the authorities have dismantled around 20 such camps around the city, taking migrants to refugee hostels, hotels or gyms acting as temporary migrant centres.
Hidalgo said it was time for a “change of tack”.
“That means setting up a reception centre where migrants can rest and get a medical check-up and psychological help as well as advice on their status and what they can expect,” she said.
“If we need to create other sites, we’ll do it,” she added.
Around 80,000 people applied for asylum in France last year, 20,000 more than in 2014, but only a fraction of the one million asylum requests received by Germany.