Palazzo Isimbardi, Administrative palace in Milan, Italy.

Palazzo Isimbardi is a historic palace at 35 Corso Monforte in central Milan, seat of the Metropolitan City of Milan. Its 18th-century street facade has two floors with stucco friezes and cornices, a stone portal and a balcony with balusters. Inside, a square courtyard is surrounded by a Doric granite colonnade with round arches.

The palace's earliest core is said to date from the 15th century as the residence of Cicco Simonetta, councillor to Francesco Sforza. It passed to the Pallavicino family, then to the Taverna in the mid-16th century, and in 1607 the fugitive Gian Paolo Osio was killed in its basements. Acquired by the Lambertenghi in 1731 and then by the Isimbardi, it was sold in 1908 to Franco Tosi and in 1935 to the province of Milan.

The palace's name comes from the Isimbardi family, who bought it in 1731 and kept it until Luigi Isimbardi died without heirs in 1908. Inside, the Sala degli affreschi holds works by Morazzone, the Sala Giunta has a fresco by Giambattista Tiepolo, and another room displays Francesco Hayez's Episodio dei Visconti. Tradition holds that the ghost of Gian Paolo Osio, killed in the basement in 1607, still wanders the cellar.

Since the building functions as a government office, access inside is generally limited to official business, but the facade and courtyard can be seen from the street without any restriction. During open-door civic events, entry to some rooms may be possible.

In 1607 the nobleman Gian Paolo Osio, lover of the nun of Monza and author of several crimes, took refuge here hoping for hospitality from the Taverna family, who killed him in the basement. Tradition holds that his ghost still wanders the cellar.