The plaque was placed on the façade of the house at 25 Nowy Świat St., which belonged to Frassati-Gawrońska before the war.
She received the house in 1926 as a gift from her father, Alfredo Frassati, a senator and founder of the La Stampa daily newspaper.
A year earlier, she married Polish diplomat Jan Gawroński, who served as secretary to the Polish ambassador to Italy and the Vatican.
She was 23 at the time and held a law degree from the University of Turin.
The inscription on the plaque describes Frassati-Gawrońska as "the Italian woman who fell in love with Poland," adding that she rendered services to Poland during World War II and was the sister of St. Pier Giorgio Frassati.
The plaque was unveiled by Frassati-Gawrońska's three daughters: Wanda, Maria Grazia and Giovanna.
Speaking to the media, Wanda Gawrońska said the importance of what her mother did for Poland "cannot be overestimated."
She said one of her mother’s greatest achievements was intervening with Italian leader Benito Mussolini to secure the release of a large group of professors from Poland's Jagiellonian University and other institutions of higher education in the southern city of Kraków who had been arrested by the Germans during the infamous Sonderaktion Krakau operation on November 6, 1939.
According to historians, of the 144 academics arrested at the time, 101 were released following a request by Mussolini and Italian Foreign Minister Galeazzo Ciano.
Thursday's ceremony in Warsaw was also attended by the apostolic nuncio to Poland, Archbishop Antonio Guido Filipazzi; the Italian ambassador to Warsaw, Luca Franchetti Pardo; and Polish foreign ministry officials.
The Italian ambassador described Frassati-Gawrońska as an "extraordinary figure of the 20th century who, through her example and constant civic commitment, bore witness to the deep and enduring friendship that unites Italy and Poland, as well as the values of solidarity, generosity and altruism."
"As the Italian ambassador to Poland, I consider myself to be a spokesman for the links of common heritage of our two nations and for the stature of this great personality, bearing in mind not only her World War II record but also the postwar period, when the Gawroński family remained committed to providing assistance to those in need," he said.
Prior to World War II, Frassati-Gawrońska lived in Austria, where her husband served as Poland's ambassador, the last to hold the post before Austria was annexed by Nazi Germany in 1938.
The couple subsequently moved to Warsaw.
After Germany invaded Poland in 1939, Frassati-Gawrońska became active in the Polish resistance movement. Her Italian passport allowed her to travel freely around Europe.
In one of her most daring exploits, she helped the wife of Gen. Władysław Sikorski leave Poland.
On Christmas Eve 1939, the woman left Warsaw with Frassati-Gawrońska posing as her nanny. In early January 1940, she reunited with her husband, then prime minister of the Polish government-in-exile in Paris.
In all, Frassati-Gawrońska made seven missions to occupied Poland as an emissary of the Polish government-in-exile.
After the war, Frassati-Gawrońska lived in Rome. She described her wartime experiences in the book Il destino passa per Varsavia.
She also wrote books about her father and her brother Pier Giorgio, who died of polio at age 24 and was canonised in 2025.
In 1993, she received the Polish Order of Merit for her services to the country.
She died in 2007 in her native village of Pollone in northern Italy at the age of 105.
(mk/gs)