Tullia d'Aragona (1501/1505 – March or April 1556) was an Italian poet, author, and philosopher. Born in Rome sometime between 1501 and 1505, Tullia traveled throughout Venice, Ferrara, Siena, and Florence before returning to Rome. Throughout her life, Tullia was esteemed one of the best female writers, poets, and philosophers of her time. Influencing many of the most famous philosophers, Tullia's work elevated women's status in literature to equal that of men. Her intellect, literary abilities, and social graces helped her become among the most celebrated of Renaissance poet-courtesans.

Tullia was born in Rome sometime between 1501 and 1505, to Giulia Campana (formerly Giulia Pendaglia), daughter of the otherwise unknown Orsino Pendaglia from Ferrara. Also known as Giulia Ferrarese, Tullia's mother was lauded as "the most famous beauty of her day." A floor tomb in the Church of S. Agostino in Rome confirms her mother's last name as Campana. It is unknown if Tullia's maternal grandfather was a member, natural or legitimate, of a noble Ferrarese family with the same name.

There is some controversy surrounding who fathered Tullia. A document in Siena identifies her father as Costanzo Palmieri d'Aragona from Naples. Tullia and her admirers claim her father is in fact Cardinal Luigi d'Aragona, the illegitimate grandson of Ferdinando d'Aragona, King of Naples. Some have speculated that Giulia's marriage to Costanzo Palmieri d'Aragona was a cover-up orchestrated by Cardinal Luigi d'Aragona's family to hide his liaison. This allowed him to continue to frequent her without interference. Some researchers have inferred that this was a way for the family to save face. Because Tullia's mother was not married to her father, Tullia's life was marked by the stigma of her illegitimate birth to a courtesan mother.

Nevertheless, the Cardinal provided Tullia with a classical education in the humanities. Young Tullia proved to be a child prodigy who amazed even her mother's 'guests.' Tullia spent the first part of her childhood in Rome, but around the time of the Cardinal's departure for his well-known journey through northern Europe, she and her mother moved to Siena.

While in Siena, Tullia's mother married Africano Orlandini from the noble Orlandini family. There are accounts of Tullia returning to Rome in 1524, which is when she was immortalized in a madrigal by Philippe Verdelot. By June 1526, Tullia was confirmed to have returned to Rome in the company of the Florentine banker Filippo Strozzi, as written in a letter from Strozzi to Francesco Vettori. Tullia and Strozzi spent many years together traveling throughout Italy until his suicide in 1538.

Entering into the world as courtesan at age 18, Tullia became successful as a writer and an intellectual. She was often seen in the company of poets, such as Sperone Speroni. After the Cardinal's death in 1519, Tullia spent seven years in Siena, before she returned to Rome in 1526. Available evidence suggests that she was highly mobile and stayed in Bologna in 1529, where Pope Clement VII and Holy Roman Emperor Charles V were engaged in negotiations after the Sack of Rome in 1527.

In 1531, she became involved with Filippo Strozzi, a Florentine banking magnate who had been famous for a short-lived affair with Italy's most beautiful courtesan, Camilla Pisana. Strozzi became so enamored with d'Aragona that he shared state secrets with her and had to be recalled to Florence. Other lovers included Emilio Orsini, who founded a Tullia Society of six cavaliers who protected her honor.

In 1535, Penelope d’Aragona was born in Rome. Scholars debate whether Penelope d'Aragona was Tullia's daughter (Tullia at the time was 25 years old), or her sister, as the family claimed.