Sant'Apollonia was the demolished 16th century church of a convent of Franciscan nuns in Trastevere. The location was in the Piazza di Sant'Apollonia, opposite Santa Margherita and just east of Santa Maria in Trastevere.
The convent of sisters of the Third Order of St Francis was founded by one Paluzza Pierleoni in her palazzo on the site in the early years of the 15th century. At first this seems to have been an informal community, but the patroness obtained recognition of it from Pope Nicholas V in 1458. The pope conceded that the sisters (part of a religious movement known as bizoche in Italian, corresponding to beguines in northern Europe) could live without enclosure, but Pope Pius V (who had no time for bizoche) annulled this and forced the sisters to become enclosed nuns.
The convent was rebuilt in 1582, and in the process incorporated two little churches close to each other: Sant'Apollonia dell'Olivo and San Cristoforo. The latter was demolished. One confusing reference from the time of Pope Pius mentions a convent of Franciscan nuns called Santa Maria dell'Olivo. This old title of Our Lady has been remembered, and re-used for a suburban church: Santa Maria dell’Olivo. It is considered to have been referring to Sant'Apollonia, since it rather stretches the credulity to posit a third convent of Franciscan nuns in the locality. The second convent was Santa Margherita di Antiochia, and these two communities of Franciscan nuns survived opposite each other until the end of the 18th century.
Romans with toothache used to pray in the church here for relief, since St Apollonia was a martyr of Alexandria in Egypt who had had her teeth pulled out with pliers before being burned.
After the expropriation of the nunnery by the State in 1873, the church was demolished and replaced by an apartment block in 1888. However, some old masonry from the convent seems to have been incorporated into the buildings on the site.
The site of this lost church is easy to locate, since the modern building on the north side of the Piazza di Sant'Apollonia is exactly on its footprint.
This was a small church, and the piazza frontage of the building there now corresponds to the left hand nave wall in its entirety. The plan was on a rectangle, with a nave of three bays separated by two pilasters on each side that supported the ceiling vault. There was a small square apse with a triumphal arch.
The façade had two storeys, the second (excluding the pediment) being about two-fifths the height of the first. The latter had four Doric pilasters on very high plinths, supporting an entablature with a projecting cornice. The tall single entrance was approached by a short flight of steps, and above the marble doorcase was a length of entablature matching that of the main one of the storey. Above the entrance was a large tondo containing a fresco of St Apollonia, holding a pair of pincers with one of her teeth in it. On the lintel of the doorcase was a short dedicatory inscription: Ecclesia S[anctae] Clarae et S[anctae] Apolloniae V[irginis] et M[artyris]. The nuns included St Clare, the foundress of Franciscan nuns, in the dedication after the 1582 rebuilding.
In between the pairs of pilasters were two arched niches, with a pair of little pilasters each. These niches had a recessed square panel above and below.
The short second storey had a transverse rectangular window, almost square, with a relief frame within a sunk rectangular panel. Two other such panels flanked it. Above was the crowning triangular pediment.
The interior had three side altars. The main altar had an altarpiece showing St Apollonia with SS Francis and Clare, and above this was a depiction of the Assumption. The vault of the apse had a fresco of the Trinity being venerated by angels. The side altars were dedicated to the Immaculate Conception, St Peter of Alcantara and St Christopher. The second had an altarpiece showing the saint talking to St Teresa of Avila (they were great friends), and the last one recalled the demolished church of St Christopher. It contained an old fresco of the saint, rescued at the demolition.