Piazza di Pietra, Ancient Roman square in central Rome, Italy

Piazza di Pietra is a square in the Colonna district of Rome, linked to Via del Corso. It is dominated by the colonnade of the Temple of Hadrian, erected by Antoninus Pius in honour of his adoptive father. At the end of the 17th century Carlo Fontana incorporated the colonnade into the Dogana dei Beni di Terra, later the Stock Exchange and now the Chamber of Commerce. Palazzo Ferrini Cini and the Collegio dei Bergamaschi also face the square.

The site originated as a temple built in the 2nd century AD to honor Emperor Hadrian, with construction commissioned by his successor. Over the following centuries, the area was built over many times, yet portions of the original temple's columns remained visible and were preserved within new structures.

The square's name comes from the people, likely from the size of the colonnade's stones; it was earlier called Piazza dei Preti after a hospice for invalid priests run by the Ospizio di San Michele. Today the colonnade fronts the Rome Chamber of Commerce, and the square also faces Palazzo Ferrini Cini and the Collegio dei Bergamaschi.

The square opens off Via del Corso in the Colonna district, a short walk from the Pantheon. It is a pedestrian space, so visitors can stand directly beneath the eleven columns. The colonnade faces the open square and is best seen from the far side, where the full row comes into view.

The square's earlier name, Piazza dei Preti, came from an Ospizio dei Preti invalidi, a hospice for invalid priests dependent on the Ospizio di San Michele, that stood here. The present name is popular in origin and most likely refers to the size of the colonnade's stones.