The installation of Christian churches in the Roman Forum undoubtedly constitutes the most marked evidence of the Christianization of the Roman Forum among other transformations which in part helped the political-monumental center of the city survive and rewrite its centrality up until the early Middle Ages.

The study of the location of the cult places established in the Roman Forum shows a complex network of churches and oratories founded at various times over a period of about six centuries from the sixth to the eleventh, with a major boom between the sixth and eighth centuries CE. For the most part these were installed in either pre-existing buildings completely or partially reusing ancient monuments. These structures generally track the chronology of progressive abandonments, structural reuse, and in most cases entail architectural additions and adaptations.

This dominant trend allows us to see the establishment of Christianity in Rome as a crucial transforming factor within the processes of disintegration of the ancient city. During the centuries of imperial (starting circa 312/313 CE), Gothic and Byzantine Rome (before the later and more radical administrative and institutional changes), this did not entail the precocious alienation and 'privatization' of public spaces. The overall conservation of some of the political functions of the Roman Forum and the fact that many religious buildings are the outcome of programs promoted by the governing élites of the time, often in agreement with the bishop of Rome ensured a general continuity of jurisdiction on the part of the central power.

circa 141-400 CE

San Lorenzo in Miranda
The church of San Lorenzo in Miranda, dedicated to Saint Lawrence, a 3rd-century CE Roman deacon and martyr, was established during the medieval period within the ancient cella of the Temple of Antoninus and Faustina. The original temple, constructed in 141 CE by Emperor Antoninus Pius to honor his deceased wife Faustina, was later rededicated to both Antoninus and Faustina by senatorial decree upon the emperor's death. This rededication is marked by the inscription DIVO ANTONINO ET DIVAE FAVSTINAE EX S C (literally translating to "To the divine Antoninus and the divine Faustina, by decree of the Senate") still visible on the temple's architrave.

By the 11th century CE, the church was being mentioned as San Lorenzo in Miranda, a name believed to derive from the Latin term miranda, meaning "things worthy of admiration", possibly referencing the commanding view of the Forum it overlooks. In 1429 CE, Pope Martin V entrusted the church to the Collegio degli Speziali (College of Chemists and Herbalists), designating it as a center for study and charitable activities.

Between 1601 and 1614 CE, the church underwent extensive renovations under the direction of architect Orazio Torriani. The façade, constructed in two levels using brick, integrates ten of the original Corinthian columns of the ancient Roman period temple, creating a monumental portico. The interior of the church features a single nave with three chapels on either side. It houses notable 17th-century CE artworks, including Pietro da Cortona's Martyrdom of Saint Lawrence on the high altar and Domenichino's Madonna with Child and Saints in the left chapel.

Architecturally and historically significant, the transformation of San Lorenzo in Miranda reflects both the adaptive reuse of pagan temples for Christian worship and the evolution of ecclesiastical architecture during the Renaissance and Baroque periods. The building remains associated with the Nobile Collegio Chimico Farmaceutico Universitas Aromatoriarum Urbis, preserving its historical ties to the study and practice of pharmaceutical arts.

circa 450 CE

Church of Santa Maria Antiqua
The church of Santa Maria Antiqua, situated on the slopes of the Palatine Hill, is the earliest and most significant Christian church in the Roman Forum. Established in the mid-6th century CE within a Domitianic architectural complex, it represents a crucial phase in the Christianization of Rome and stands as a pivotal monument in the development of Byzantine-influenced religious art in the ancient city. The church was abandoned after suffering extensive damage in an 847 CE earthquake, following which a new structure, Santa Maria Liberatrice, was erected over the ruins in the 13th century CE. The Baroque restoration by Onorio Longhi in subsequent centuries was reversed in 1899 CE when the later church was demolished to reveal the earlier sacred site.

The church's architectural layout features a central nave flanked by side aisles and a presbytery with two chapels on either side. Approximately 250 square meters of frescoes remain visible, dating from the 6th to the 9th centuries CE, offering a layered narrative of artistic and religious expression. These frescoes, frequently superimposed over older works, form a visual palimpsest that reveals evolving iconographic trends. One of the earliest depictions shows the Virgin Mary enthroned as a Roman empress with the Christ-child, dating from the church's initial phase. Another notable work is the Annunciation, featuring the celebrated "Beautiful Angel", created in the 7th century CE. The chapel of Theodotus, commissioned during the papacy of Pope Zacharias (741–752 CE), contains a near-complete cycle illustrating the martyrdom of Saints Cyricus and Julitta. Adjacent to the presbytery, a chapel honors the Medici Saints, while the left aisle features rows of saints from both the Greek and Latin traditions, accompanied by Old Testament narratives.

A striking feature near the church entrance is the Domitian Ramp, a monumental structure originally connecting the Forum to the Palatine palaces. With the Forum's Christianization, this space was transformed into an oratory dedicated to the Forty Martyrs of Sebaste, early Christian soldiers martyred in Armenia during the imperial persecutions of the early 4th century CE. The oratory preserves an 8th-century fresco commemorating their martyrdom. Additional frescoes, including an image of Saint Anthony the Hermit, adorn the quadrangular interior. Fragments of medieval marble paving remain, further testifying to the site's complex history and ongoing transformation during Rome's Christian era.

circa 500 CE

Church of Santi Sergio e Bacco al Foro Romano
The church of Santi Sergio e Bacco al Foro Romano, also simply known as Santi Sergio e Bacco sub Capitolio, was an ancient titular church in Rome dedicated to the fourth-century martyrs Sergius and Bacchus. Located in the Roman Forum, it served as a diaconia and a station for Lent processions. The church, founded in the 7th century, underwent significant expansion under Pope Gregory III, but fell into disrepair by the 8th century. It was renovated by Pope Innocent III, but ultimately demolished in the 16th century. The church's exact destruction remains debated, with some sources attributing it to Pope Paul III for a triumphal march.

circa 500 CE

Church of Santa Salvatore de Stadera al Foro Romano
The church of Santa Salvatore de Stadera, was installed in the Temple of saturn.

circa 527 CE

Church of Saints Cosmas and Damian
The basilica or church of Saints Cosmas and Damian (Chiesa dei Santi Cosma e Damiano) is a titular church in the Roman Forum of Rome, Italy. It is the conventual church of the General Curia of the Franciscan Third Order Regular. The lower portion of the building is accessible from the Roman Forum through the Roman temple of Romulus and incorporates original Roman buildings, but the entrance to the upper level is outside the Forum facing the Via dei Fori Imperiali. Today it is one of the ancient churches called tituli, of which cardinals are patrons as cardinal-deacons. Since 28 November 2020 CE the title has been held by Cardinal Mario Grech. The basilica, devoted to the two Arabian Christian brothers, doctors, martyrs and saints Cosmas and Damian, is located in the Forum of Vespasian, also known as the Tempio della Pace (Forum of Peace).

circa 630 CE

Church of Sant'Adriano al Foro
The church of Sant'Adriano al Foro, literally meaning the Saint Hadrian at the Forum, originally the Curia Julia in the Roman Forum, repurposed by Pope Honorius I in 630 CE. It was dedicated to St. Adrian of Nicomedia, and by the 7th century, became a site for liturgical processions. The church underwent modifications by Pope Gregory IX in 1228, with the relics of saints Papias and Maurus transferred in 1590. Deconsecrated in the 1930s, its structure was restored, with significant artwork relocated to other churches. The church's history reflects the city's medieval decay and subsequent revitalization.

circa 630 CE

Church of Santi Luca e Martina
The church of Santi Luca e Martina, a church located in the heart of Rome between the Roman Forum and the Forum of Caesar, holds a rich historical and architectural significance. Originally dedicated to Saint Martina, a martyr from the 3rd century, it underwent significant transformations over the centuries. Pope Honorius I commissioned its construction in 625, though it was later restored and expanded, particularly in the 17th century, under the direction of renowned painter and architect Pietro da Cortona.

The church was initially a modest structure but was enlarged and redesigned after being given to the Accademia di San Luca, an esteemed academy for painters, sculptors, and architects, in 1588. This institution’s influence is particularly evident in the church's redesign during the tenure of Cortona, who aimed to create a space that both honored Saint Luke, the patron saint of artists, and provided a suitable location for the academy's activities. The upper church is designed in a Greek cross plan, with the dome as its central focal point. Cortona's intricate design features large Ionic columns, an entablature that frames the nave and transepts, and a combination of classical motifs that merge with the grandiose painting and decoration of the church.

The interior is a testament to Cortona's artistic prowess, with the dome’s decoration attributed to his pupil, Ciro Ferri, featuring a fluid and almost ethereal design. The lower church, in contrast, is more intimate and opulent, with a richly decorated chapel dedicated to Saint Martina, who was martyred in the early 3rd century. The lower church contrasts the upper's brightness with its darker, more ornamental interior that includes a collection of colorful marbles, gilt bronze, and a notable relief of Saint Mary Magdalene's Ecstasy by Alessandro Algardi.

The church also contains several important works of art, including altarpieces and sculptures by well-known artists such as Sebastiano Conca, Antiveduto Grammatica, and Lazzaro Baldi. A notable feature of the church is its connection to various artists, as Cortona himself is buried here, with a commemorative plaque marking his resting place. Throughout its history, Santi Luca e Martina has served not only as a place of worship but as a center for artistic and architectural development, encapsulating the dynamic interplay between religious devotion and artistic expression that defined much of Rome's Baroque period.

circa 750-950 CE

Church of Santa Francesca Romana
The church of Santa Francesca Romana, also known as the Basilica di Santa Francesca Romana, originally known as Santa Maria Nova, is a Catholic church located next to the Roman Forum. The site, historically significant, was purportedly the location where Saint Peter prayed to challenge Simon Magus, resulting in Simon's fall. By the tenth century, a church was established here, later rebuilt in the thirteenth century under Pope Honorius III, who added a campanile, apse, and a mosaic of the Madonna. In the 16th century, the church was rededicated to Saint Frances of Rome. Since 1352, the Olivetans have cared for the church, and it has undergone several refurbishments, including the addition of a travertine façade in 1615 designed by Carlo Lambardi.

The interior of the church is characterized by a single nave with side chapels and is enriched by various altarpieces, including works by Pietro Tedeschi and Padre Pozzi. The sacristy houses the Madonna Glycophilousa, an early 5th-century icon, and the tomb of Pope Gregory XI. The church's historical significance extends beyond its religious function, as it was the site of papal restoration efforts and later became the titular church for a Cardinal Priest. Santa Francesca Romana is also associated with the patronage of car drivers due to a legend of an angel lighting Saint Frances' way at night. The church's influence is even evident in the design of the Church of Holy Cross College in Dublin, which features a replica of its façade.

circa 1663 CE

Church of San Giuseppe dei Falegnami
The church of San Giuseppe dei Falegnami, also known as the Basilica di Santa Francesca Romana, located next to the Roman Forum, was originally built in the 11th century as Santi Pietro e Paolo in Carcere over the Mamertine Prison, a site historically associated with the imprisonment of Saints Peter and Paul. In 1540, the Congregation of the Carpenters began construction of the current church, which was completed in 1663. The church features a nave with side chapels, and its interior includes paintings by Carlo Maratta. Notably, in 1853, the Chapel of the Crucifix was built between the church's floor and the prison ceiling. Following significant restoration work, the church was elevated to titular status in 2012.

In 2018, the church suffered a ceiling collapse, leading to its closure. The restoration revealed gaps in the understanding of coffered ceiling construction methods. Over the centuries, the church underwent various renovations, including a new apse in 1886 and an elevation of the façade in the 1930s to provide access to the Mamertine Prison. The church's oratory, with its wooden ceiling, remains a notable feature of the complex.