Each "homeless pilgrim," as the Vatican called the clients, will receive a kit including a towel, change of underwear, soap, deodorant, toothpaste, razor and shaving cream.
The showers will be open every day except Wednesday, when the piazza is full for the pope's general audience.
Haircuts will be available on Mondays.
Barbers volunteering on their days off - Rome's barber shops are closed on Mondays - as well as students from a local beauty school will be donating their time, as well as some sisters from religious orders and other volunteers.
The bathrooms were made with high-tech, easy-to-clean materials to ensure proper hygiene, the Vatican said in a statement. The walls are grey, with white washbasins and a high-tech looking barber chair.
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Francis' chief alms-giver, Monsignor Konrad Krajewski, has said the project is needed since homeless people are often shunned for their appearance and smell.
The initiative is being funded by donations and sales of papal parchments sold by Krajewski's office.
Francis has stepped up the role of the Vatican "elmosiniere" as part of his insistence that the church look out for the poorest.
In addition to small acts of charity, Krajewski's office handed out 400 sleeping bags to the homeless over Christmas, distributed 1600 phone cards to new migrants on the island of Lampedusa, and this past week gave away about 300 umbrellas that had been left behind at the Vatican Museums to help the homeless cope with days of heavy rain in the capital.
