Piazza San Marco (Italian pronunciation: [pjattsa sam marko]; Venetian: Piasa San Marco), often known in English as St Mark's Square, is the principal public square of Venice, Italy, where it is generally known just as la Piazza ("the Square"). All other urban spaces in the city (except the Piazzetta and the Piazzale Roma) are called campi ("fields"). The Piazzetta ("little Piazza/Square") is an extension of the Piazza towards San Marco basin in its south east corner (see plan). The two spaces together form the social, religious and political centre of Venice and are commonly considered together. This article relates to both of them.

A remark usually attributed (though without proof) to Napoleon calls the Piazza San Marco "the drawing room of Europe".

St Mark's Campanile (Italian: Campanile di San Marco, Venetian: Canpanièl de San Marco) is the bell tower of St Mark's Basilica in Venice, Italy. The current campanile is a reconstruction completed in 1912, the previous tower having collapsed in 1902. At 98.6 metres (323 ft) in height, it is the tallest structure in Venice and is colloquially termed "el paròn de casa" (the master of the house). It is one of the most recognizable symbols of the city.Located in Saint Mark's Square near the mouth of the Grand Canal, the campanile was initially intended as a watchtower to sight approaching ships and protect the entry to the city. It also served as a landmark to guide Venetian ships safely into harbour. Construction began in the early tenth century and continued sporadically over time as the tower was slowly raised in height. A belfry and a spire were first added in the twelfth century. In the fourteenth century the spire was gilded, making the tower visible to distant ships in the Adriatic. The campanile reached its full height in 1514 when the belfry and spire were completely rebuilt on the basis of an earlier Renaissance design by Giorgio Spavento. Historically, the bells served to regulate the civic and religious life of Venice, marking the beginning, pauses, and end of the work day; the convocation of government assemblies; and public executions.

The campanile stands alone in the square, near the front of St Mark's Basilica. It has a simple form, recalling its early defensive function, the bulk of which is a square brick shaft with lesenes, 12 metres (39 ft) wide on each side and 50 metres (160 ft) tall. The belfry is topped by an attic with effigies of the Lion of St Mark and allegorical figures of Venice as Justice. The tower is capped by a pyramidal spire at the top of which there is a golden weather vane in the form of the archangel Gabriel.