Philadelphia City Hall is the seat of the municipal government of the City of Philadelphia in the U.S. state of Pennsylvania. Built in the ornate Second Empire style, City Hall houses the chambers of the Philadelphia City Council and the offices of the Mayor of Philadelphia.

Second Empire style, also known as the Napoleon III style, is a highly eclectic style of architecture and decorative arts, which uses elements of many different historical styles, and also made innovative use of modern materials, such as iron frameworks and glass skylights. It flourished in the Second French Empire during the reign of Emperor Napoleon III (1852–1870) and had an important influence on architecture and decoration in the rest of Europe and North America. Major examples of the style include the Opéra Garnier (1862–1871) in Paris by Charles Garnier, the Bibliothèque nationale de France, the Church of Saint Augustine (1860–1871), and the Philadelphia City Hall (1871–1901). The architectural style was closely connected with Haussmann's renovation of Paris carried out during the Second Empire; the new buildings, such as the Opéra, were intended as the focal points of the new boulevards.