She was born Catherine Benin in   Siena, Italy, to Giacomo di Benincasa, a clothdyer, and Lapa Piagenti, possibly daughter of a local poet. Born in 1347, she was the last of 25 children. She took the habit of the Dominican Tertiaries after vigorous protests from the Tertiaries themselves.

In about 1366, St Catherine experienced what she described in her letters as a "Mystical Marriage" with   Jesus. Her biographer   Raymond of Capua   also records that she was told by Christ to leave her withdrawn life and enter the public life of the world. Catherine dedicated much of her life to helping the ill and the poor, where she took care of them in hospitals or homes. Her early pious activities in Siena attracted a group of followers, both women and men, while they also brought her to the attention of the Dominican Order, which called her to Florence in 1374 to interrogate her for possible heresy. After this visit, in which she was deemed sufficiently orthodox, she began travelling with her followers throughout northern and central Italy advocating reform of the clergy and the launch of a new crusade and advising people that repentance and renewal could be done through "the total love for God." ^{[ 1 ]}

Physical travel was not the only way in which Catherine made her views known. In the early 1370s, she began writing letters to men and women of her circle, increasingly widening her audience to include figures in authority as she begged for   peace   between the republics and principalities of Italy and for the return of the   Papacy   from   Avignon   to   Rome. She carried on a long correspondence with   Pope Gregory XI, also asking him to reform theclergy   and the administration of the   Papal States.

In June of 1376 Catherine went to   Avignon   herself as ambassador of   Florence   to make peace with the   Papal States, but was unsuccessful. She also tried to convince   Pope Gregory XI   to return to Rome. ^{[ 2 ]}   She impressed the   Pope   so much that he returned his administration to Rome in January, 1377. Following Gregory's death and during theWestern Schism   of 1378 she was an adherent of   Pope Urban VI, who summoned her to Rome, and stayed at   Pope Urban VI's court and tried to convince nobles and cardinals of his legitimacy. She lived in Rome until her death in 1380. The problems of the Western Schism would trouble her until the end of her life.

St. Catherine by   Tiepolo, c. 1746

St Catherine's letters are considered one of the great works of early Tuscan literature. More than 300 letters have survived. In her letters to the Pope, she often referred to him affectionately as "Papa" or "Daddy" ("Babbo" in Italian). Other correspondents include her various confessors, among themRaymond of Capua, the kings of France and Hungary, the infamous mercenary   John Hawkwood, the Queen of Naples, members of the Visconti family of Milan, and numerous religious figures. Roughly one third of her letters are to women. Her other major work is   "The Dialogue of Divine Providence,"   a dialogue between a soul who "rises up" to God and God himself, and recorded between 1377 and 1378 by members of her circle. Often assumed to be illiterate, Catherine is acknowledged by Raymond in his life of her as capable of reading both Latin and Italian, and another   hagiographer, Tommaso Caffarini, claimed that she could write.

St Catherine died of a stroke in Rome, the spring of 1380, at the age of thirty-three. The people of Siena wished to have her body. A story is told of a miracle whereby they were partially successful: Knowing that they could not smuggle her whole body out of Rome, they decided to take only her head which they placed in a bag. When stopped by the Roman guards, they prayed to St Catherine to help them, confident that she would rather have her body (or at least part thereof) in Siena. When they opened the bag to show the guards, it appeared no longer to hold her head but to be full of rose petals. Once they got back to Siena they reopened the bag and her head was visible once more. Due to this story, St Catherine is often seen holding a   rose. The incorruptible head and thumb were entombed in the Basilica of   San Domenico, where they remain.

Saint Catherine's body is buried in the   Basilica   of   Santa Maria sopra Minerva   in Rome, which is near the   Pantheon.

Saint Catherine by   Carlo Dolci

Pope Pius II   canonized   St Catherine in the year 1461. Her   feast day, at the time, was not included in the   Roman Calendar. When it was added in 1597, it was put on the day of her death, April 29, as now, but because of a conflict with the feast of Saint   Peter of Verona, which was also on April 29, it was moved in 1628 to the new date of April 30. ^{[ 3 ]}   In the 1969 revision of the   Roman Catholic calendar of saints, it was decided to leave the celebration of the feast of St Peter of Verona to local calendars, because he was not as well known worldwide, and Saint Catherine's feast was restored to its traditional date of April 29. ^{[ 4 ]}   Some continue to use one or other of the calendars in force in the 1628-1969 period.

On 5 May 1940   Pope Pius XII   named her a joint   Patron Saint   of   Italy   along with   Saint Francis of Assisi.   Pope Paul VI   gave her the title of Doctor of the Church in 1970 along with   Saint Teresa of Ávilamaking them the first women to receive this honour. In 1999,   Pope John Paul II   made her one of Europe's patron saints.