The territory of Oristano is very rich in archaeological documentation from prehistoric times. Formed on a center of Byzantine origin, the city was the capital of the Giudicato di Oristano and maintained its importance even in the following centuries.
In Sardinia, the Franciscan Order has been present since 1230 and in 1253 the convent of Saint Francis was already established in Oristano. There is no documentary news about the church's Gothic factory. At the beginning of the nineteenth century, it was in a serious state of decay, so much so that Archbishop Giovanni Maria Bua decided to have it rebuilt from scratch, rather than restored. So in 1835 it was destroyed and on February 17 of the following year, the foundation stone of the new church was blessed, which was to be built on a design by the Sassari friar Antonio Cano, a protégé of the royals who had studied at the Accademia di San Luca in Rome. The building collapsed on September 18, 1838, before the dome was erected. From the relief that still remains of the church-convent complex and its surroundings, it can be deduced that the dome had an elliptical shape, as was customary for the works of the Cano. A short time later, the assignment passed to the most important Sardinian architect of the 19th century, Gaetano Cima, from Cagliari. The project, delivered on September 18, 1841, was approved on April 22, 1842; then work began. The building, rebuilt according to the forms of purist Classicism, was reopened for worship in October 1847.
Only a few wall structures included in the convent can be assigned to the first half of the 13th century, such as a stretch of wall made of bichromous rows of volcanite and sandstone ashlars, which houses a single window with an ogival rib doubly trumped. To the last quarter of the same century, the cloister portal, an ogival with a diamond-pointed eyebrow, and the wide lights arranged in the façade of the monastery towards the cathedral, in a semicircular rib with an inclined ring, are ascribed to the last quarter of the same century.
Also in the last quarter of the 13th century, the façade of the church dates back to the last quarter of the 13th century, of which the lower portion s., 8.63 m wide, in medium-sized volcanite and limestone ashlars, sandwiched between the median mirror that housed the portal and the parasta in the left corner. It is based on a plinth with a shoe and has a small column, with a capital, like those of the corner pillows, inserted along the edge of the corner pillar. The wall surface was divided into three mirrors by arches on beam columns. In the mirror there are the remains of a statue; in the middle one was the portal. The ornate oval arches that surmount the mirrors have Gothic moldings. The left arch is covered at the top by a tympanated frame, while the right one by an arched eyebrow, decorated with plant motifs.
The current building has a central plan, with two chapels on each side and a deep semicircular apse. From the chapel on the left, through a small room, you can access the sacristy. The façade, accessed by a wide staircase of eight steps, is preceded by a tympanated pronaos, which is based on four columns and two pillars. All supports are surmounted by Ionic capitals. The façade houses a large median portal and two smaller symmetric lateral ones. The central body of the building is covered by a large hemispherical dome, set on a cylindrical drum and surmounted by a polygonal lantern.

History of studies
The church is the subject of brief sheets in the volumes of the series “History of Art in Sardinia” on Romanesque (1993), late seventeenth-century and purist (1992) architecture.

Bibliography
V. Angius, entry “Oristano”, in G. Casalis, Historical, Statistical and Commercial Geographical Dictionary of the States by H.M. the King of Sardinia, XIII, Turin, G. Maspero, 1845;
D. Scano, History of Art in Sardinia from the 11th to the 14th Century, Cagliari-Sassari, Montorsi, 1907; R. Delogu, The Architecture of the Middle Ages in Sardinia, Rome, The State Library, 1953; R. Bonu, Oristano in its Cathedral and its churches, Cagliari, Fossataro, 1973; Saiu Délogu, The Architecture of the Middle Ages in Sardinia, Rome, The State Library, 1953; R. Bonu, Oristano in its Cathedral and its churches, Cagliari, Fossataro, 1973; Saiu Délogu, The Architecture of the Middle Ages in Sardinia, Rome, The State Library, 1953;
R. Bonu, Oristano in its Cathedral and its churches, Cagliari, Fossataro, 1973; Saiu Délogu, The Architecture of the Middle Ages in Sardinia, Rome, The State Library, 1953; R. Bonu, Oristano Idda, “The ancient portal of the cloister of S. Francesco in Oristano”, in Biblioteca Francescana Sarda, I, n. 1, 1987;
A. Sari, “The architectural work of Antonio Cano between the Neo-Fifteenth Century and Neoclassical rigor”, in Biblioteca Francescana Sarda, I, n. 1, 1987; S. Naitza, Architecture from the late 17th century to purist classicism. Nuoro, Ilisso, 1992, sheet 83;
R. Coroneo, Romanesque architecture from the mid-thousand to the early thirteenth century, Nuoro, Ilisso, 1993, sheet 149;
A. Pillittu, Archdiocese of Oristano, series “Churches and Sacred Art in Sardinia”, Cagliari, Zonza, 2003.