The Basilica of St. Mary of the Altar of Heaven (Latin: Basilica Sanctae Mariae de Ara coeli in Capitolium, Italian: Basilica di Santa Maria in Ara coeli al Campidoglio) is a titular basilica in Rome, located on the highest summit of the Campidoglio. It is still the designated Church of the city council of Rome, which uses the ancient title of Senatus Populusque Romanus. The present Cardinal Priest of the Titulus Sanctae Mariae de Aracoeli is Salvatore De Giorgi.

The shrine is known for housing relics belonging to Saint Helena, mother of Emperor Constantine, various minor relics from the Holy Sepulchre, both the canonically crowned images of Nostra Signora di Mano di Oro di Aracoeli (1636) on the high altar and the Santo Bambino of Aracoeli (1897).

Originally the church was named Sancta Maria in Capitolio, since it was sited on the Capitoline Hill (Campidoglio, in Italian) of Ancient Rome; by the 14th century it had been renamed. A medieval legend included in the mid-12th-century guide to Rome, Mirabilia Urbis Romae, claimed that the church was built over an Augustan Ara primogeniti Dei, in the place where the Tiburtine Sibyl prophesied to Augustus the coming of the Christ. "For this reason the figures of Augustus and of the Tiburtine sibyl are painted on either side of the arch above the high altar" (Lanciani chapter 1). A later legend substituted an apparition of the Virgin Mary.

In The History of Money, anthropologist Jack Weatherford goes into some detail about the church's previous incarnation as the temple of Juno Moneta—on the Arx—after whom Money is named.

According to Roman historians, in the fourth century B.C., the irritated honking of the sacred geese around Juno's temple on Capitoline Hill warned the people of an impending night attack by the Gauls, who were secretly scaling the walls of the citadel. From this event, the goddess acquired [the] surname-Juno Moneta, from Latin monere (to warn). . .As patroness of the state, Juno Moneta presided over various activities of the state, including the primary activity of issuing money.

. . . from Moneta came the modem English words mint and money and, ultimately, from the Latin word meaning warning.

Today, the site of the Temple of Juno Moneta, the source of the great stream of Roman currency, has given way to the ancient . . . brick church of Santa Maria in Aracoeli. Centuries ago, church architects incorporated the ruins of the ancient temple into the new building.

The church is also thought to have replaced the auguraculum, the seat of the augurs.

The foundation of the church was laid on the site of a Byzantine abbey mentioned in 574. Many buildings were built around the first church; in the upper part they gave rise to a cloister, while on the slopes of the hill a little quarter and a market grew up. Remains of these buildings - such as the little church of San Biagio de Mercato and the underlying "Insula Romana") - were discovered in the 1930s. At first the church followed the Greek rite, a sign of the power of the Byzantine exarch. Taken over by the papacy by the 9th century, the church was given first to the Benedictines, then, by papal bull to the Franciscans in 1249–1250; under the Franciscans it received its Romanesque-Gothic aspect. The arches that divide the nave from the aisles are supported on columns, no two precisely alike, scavenged from Roman ruins.

During the Middle Ages, this church became the centre of the religious and civil life of the city. in particular during the republican experience of the 14th century, when self-proclaimed Tribune and reviver of the Roman Republic Cola di Rienzo inaugurated the monumental stairway of 124 steps in front of the church, designed in 1348 by Simone Andreozzi, on the occasion of the Black Death. Condemned criminals were executed at the foot of the steps; there Cola di Rienzo met his death, near the spot where his statue commemorates him.

In 1571, Santa Maria in Aracoeli hosted the celebrations honoring Marcantonio Colonna after the victorious Battle of Lepanto over the Turkish fleet. Marking this occasion, the compartmented ceiling was gilded and painted (finished 1575), to thank the Blessed Virgin for the victory. In 1797, with the Roman Republic, the basilica was deconsecrated and turned into a stable.