The Domus Sanctæ Marthæ (English: Saint Martha's House) is a building adjacent to Saint Peter's Basilica in the Vatican City built during the reign of Pope John Paul II. It is the hotel residence of the College of Cardinals and patriarchs of the Eastern Rite taking part in the papal conclaves to elect new Popes. Its amenities include furnished bedrooms, lavatories and studies for each prelate. Dining facilities and personal services are also offered. It also functions as a guest house for those having business with the Holy See.

Prior to the Apostolic Constitution Universi Dominici Gregis — promulgated on February 22, 1996 that changed the rules governing papal conclaves — participants were forced to sleep in the Sistine Chapel on rented cots. Participants were literally sealed under lock and key in the Sistine Chapel. Pope John Paul II decided to make the process more comfortable and commissioned the construction of Domus Sanctæ Marthæ.