Of ancient foundation, the church of Sant' Agnese in Agone was rebuilt by Girolamo Rainaldi and his son Carlo, at the behest of Pope Innocent X (r. 1644-55), whose family palace stood next door. In 1653 the pair were replaced by Francesco Borromini, who added the splendid concave facade. However, he, too, was soon replaced and his work was completed by Giovanni Maria Baratta who added the twin bell towers.
The layout of the interior is based on a Greek cross plan. The seven altarpieces all take the form of bas-reliefs or statues rather than paintings. Above the main door is the funerary monument of Pope Innocent X, who is buried in the church. The high altar sports a bas-relief of The Holy Family with St John the Baptist and his Parents (1683) by Domenico Guidi. The altar is surmounted by three putti holding a bronze scroll, which reads: Non surrexit inter natos mulierum major Ioanne Baptista (None has arisen among the sons of women greater than John the Baptist), a possible reference to the pope who was born Giovanni Battista Pamphilj.
The fresco in the dome is by Ciro Ferri, a pupil of Pietro da Cortona.
A small chapel at the back of the church houses the putative skull of St Agnes.