Palazzo Erba Odescalchi, Mannerist palace in central Milan, Italy.

Palazzo Erba Odescalchi is a Mannerist palace at via dell'Unione 5 in central Milan. Its 16th-century facade by Pellegrino Tibaldi carries twelve busts of Roman emperors in the pediments of the piano nobile windows, with fragments of Gothic terracotta; the entrance portal sits slightly off the building's axis. The inner courtyard repeats the bust motif with female figures, surrounded by a Tuscan-columned arcade, and ends in a helical staircase.

The Cusani family bought a house on what was then the "contrada dei nobili", probably once held by Barnabò Visconti, and from around 1570 had it enlarged and remodelled under Pellegrino Tibaldi. In the 18th century it passed to Bishop Benedetto Erba Odescalchi, who spent his last days there. It survived the Second World War bombings without serious damage but was repeatedly altered, and it now houses Milan's II Police District.

The name Erba Odescalchi comes from Bishop Benedetto Erba Odescalchi, who owned the palace in the 18th century and spent his last days there; before that it was called Palazzo Cusani. A covered passage once linked it to the neighbouring Palazzo Caravaggio, demolished in 1877, where Ippolita Bentivoglio, natural daughter of Ludovico il Moro, lived.

The palazzo houses the II Police District (Questura) of Milan, so only the exterior can be visited. Via dell'Unione is a narrow street, and the facade cannot be taken in at a single glance; step back toward the opposite side to see the portal, which sits slightly off the building's axis. The inner courtyard and its spiral staircase belong to the police offices.

A spiral staircase in the courtyard shows innovative design from the Renaissance and connects the different levels of the building in an unusual way. This stair design was a technical and artistic achievement at the time, demonstrating both engineering skill and artistic ambition.