Philadelphia City Hall is the house of government for the city of Philadelphia, in the commonwealth of Pennsylvania. At 548 ft (167 m), including the statue of city founder William Penn atop it, it is the world's tallest masonry building, since the collapse of the pinnacle of the Mole Antonelliana in Turin, and its consequent rebuilding as a metal structure faced with stone. The weight of the building is borne by granite and brick walls up to 22 feet (6.7 m) thick, rather than steel; the principal exterior materials are limestone, granite, and marble.

It was the tallest habitable building in the world from 1901 to 1908 and the tallest in Pennsylvania until 1932 when surpassed by the Gulf Tower in Pittsburgh. It remained the tallest building in Philadelphia until the construction of One Liberty Place (1984–1987) ended the informal gentlemen's agreement that limited the height of tall buildings in the city; it is currently the 16th-tallest building in Pennsylvania.