Sant'Eustachio is a Roman Catholic titular church and minor basilica in Rome, named for the martyr Saint Eustace. It is located on Via di Sant'Eustachio in the rione Sant'Eustachio, a block west of the Pantheon and via della Rotonda, and a block east of Sant'Ivo alla Sapienza and the Via della Dogana Vecchia.
The facade was built under the direction of Cesare Corvara († 1703) with the collaboration of other architects. It consists of two sections, with the upper section standing back. The lower part is marked with four pilasters and two columns, all with Ionic capitals with in the middle of each capital a small head of a deer. The spirals of the volutes are connected by a small laurel wreath. On the right side of the facade a plaque was placed in memory of the flood of the Tiber River in 1495, whose waters reached up to the basilica.
The top section is divided by four pilasters with on each side a large volute. In the middle is a large window with an arcuated cornice, flanked on each side by a niche adorned with shells. On top is a triangular pediment with in its middle a circular window surrounded with palm branches and surmounted by a crown. On top of the pediment stands a deer head with a cross between the antlers (done by the sculptor Paolo Morelli († 1719), in reference to the legend of Saint Eustace.
An iron gate, made by Gian Battista Contini, closes off the porch. The square Romanesque campanile is situated on the back of the church at its left side. Construction was started in 1196 under the pontificate of Pope Celestine III. The top part can be dated back to the end of the 12th century, while the base is somewhat older and can be dated at ca. 1090.
The interior has a cruciform architectural plan and consists of a single nave. Its construction was carried out in mature Baroque style under the supervision of the architects Cesare Corvara and Antonio Canevari. The nave is marked on each side by three pilasters resting on a broad base. The pilasters are decked with fluted white marble and surmounted by composite capitals. The rib vault is stuccoed with flowers and leaves. The crossing is covered with a dome with a representation of the Holy Spirit in its middle.
The main altar was commissioned by Cardinal Nereo Corsini to the architect Nicola Salvi. He made it into an elegant and refined synthesis of marble and gilded metal. The top of the altar rests on an urn in porphyry rosso antico, the costly stone of the ancients, that contains the relics of Saint Eustace. The altarpiece was painted in 1727 by Francesco Ferdinandi (1679-1740), also named "l'Imperiali". It represents the martyrdom of Saint Eustace and his family who were roasted to death inside a bronze statue of a bull or an ox, in the year AD 118. The gilded wooden baldachin (circa 1746) over the main altar is attributed to Ferdinando Fuga (1699-1781).