Palazzo delle papesse, centro arte contemporanea, Renaissance palace and contemporary art center in Siena, Italy.

Palazzo della Papesse is a Renaissance palace in Siena featuring a stone facade with rusticated stonework on the ground level and two rows of paired windows on the upper stories. Inside, a courtyard displays sculptures from the early 1500s.

Caterina Piccolomini, sister of Pope Pius II, commissioned the palace in 1460 on Via di Città, probably to a design by Bernardo Rossellino, the pope's favoured architect. It was finished around 1495 with work by Antonio Federighi and Urbano da Cortona. When the Piccolomini line died out at the end of the 1600s, the family consortium leased the building to the Tolomei boarding school, which moved out in 1820.

The name "delle Papesse" comes from Caterina Piccolomini, sister of Pope Pius II, who commissioned the palace in 1460. From 1998 to 2008 it housed Siena's Centro d'Arte Contemporanea, with exhibitions by artists such as Christian Boltanski and Jaume Plensa; it reopened as an exhibition venue in 2025.

The palace is at Via di Città 126, on the street that winds above the Campo in Siena's historic centre. Visitors move through three floors, and the open terrace on the second floor looks toward the dome of Siena Cathedral. The top-floor loggia gives a panoramic view over the city roofs, the Campo and the surrounding countryside.

Galileo Galilei stayed in the palace from 9 July to December 1633 as a guest of Archbishop Ascanio II Piccolomini, and observed the moon from the roof loggia, the altana, which also gives a wide view over Siena's roofs.