The Pantheon of Agrippa, also known as the Pantheon of Rome, is an ancient Roman temple that today functions as a Catholic church. It stands on the site of a former temple commissioned by Marcus Agrippa during the rule of Augustus. Emperor Hadrian completed it and it was consecrated around the year 126. The exact date of its construction is uncertain because Hadrian chose not to inscribe the new temple and kept the inscription of the previous temple that had burned down.

The name "Pantheon" comes from the Greek "Pantheion," meaning "temple of all the gods." Most Latin authors use the Latin form of its transliteration, "Pantheon," although "Pantheum" is also attested by Pliny the Elder.

The structure is circular and has a portico featuring large granite Corinthian columns, eight in the first row and two groups of four behind, under a pediment. A rectangular vestibule connects the portico to the rotunda, which is under a concrete dome with a central opening to the sky. This dome, built almost two thousand years ago, is still the largest in the world made of unreinforced concrete. The height to the oculus and the diameter of the inner circle are identical: forty-three meters. The vaulted circular cella with a conventional portico was an innovation in Roman architecture and later became a standard that other architects imitated.

The Pantheon is one of the best preserved buildings of Ancient Rome due to its continuous use throughout history. Since the 7th century, it has been used as a church and currently bears the name "Basilica of St. Mary and the Martyrs," although it is commonly known as "Santa Maria Rotonda." The square in front of the Pantheon is called "Piazza della Rotonda" and gives its name to a district of the city.

The building is owned by the state and managed by the Ministry of Cultural Assets and Activities through the Museo Centrale del Lazio. In 2013, it attracted six million visitors.

Remains discovered in the late 19th century indicate that the original temple differed significantly from the current building. What now serves as the entrance portico was originally the façade of a peripteral temple. The original entrance was located on the opposite side, to the south, where the rotunda is today. On the other side of this circular plaza was the basilica of Neptune.

The first temple had a rectangular structure with the cella arranged transversely, similar to the temple of Concordia in the Roman Forum and the small temple of Veiove in the Campidoglio. It was built with travertine blocks and covered in marble. The capitals were of bronze and the decoration included caryatids and frontal statues. Inside the pronaos were statues of Augustus and Agrippa.

Dion Cassius reveals that the name "Pantheon" was not the official name of the building and that Agrippa intended to establish a dynastic cult, possibly dedicated to the protectors of the gens Julia: Mars, Venus and the Divus Iulius, that is, Julius Caesar divinized.

The building was damaged in a fire in 80, which was repaired by Domitian, but experienced further destruction during the reign of Trajan in 110.