A piazza is an open square in a city, often used as a marketplace, found in Italy. It is roughly equivalent to the Spanish plaza. Piazza has taken some slightly different meanings in Britain and the US. In Ethiopia, it is used to refer to a part of a city. When the Earl of Bedford developed the first privately-ventured public square built in London, Covent Garden, his architect Inigo Jones surrounded it with arcades, in the Italian fashion. Aristocratic talk about the piazza was connected in Londoners' minds, not with the square as a whole but with the arcades, which were called the "piazzas."

In the United States, in the early 19th century, a "piazza" by further esxtension became a fanciful name for a colonnaded porch.

Examples include

• Piazza San Marco