Palacio Subercaseaux, Valparaíso, 19th-century neoclassical palace in Puerto District, Valparaíso, Chile.

The Subercaseaux Building is a two-storey neoclassical structure with a mansard roof that fills an entire block in Valparaíso's Puerto district. It faces two streets and two passages, forming a continuous perimeter. Built in 1867 for General Ramón Herrera on land that once held the Hotel de L'Unión, it has been in ruins since the Serrano Street explosion and fire of 3 February 2007.

The building was constructed in 1867 and stood as a prominent landmark in the port district for many decades. Major damage from a 2007 fire and explosion caused significant deterioration to its structure and interior.

The building was erected in 1867 for General Ramón Herrera on land owned by his wife, where the Hotel de L'Unión had previously stood. Later accounts linking it to Antonio Subercaseaux and architect Fermín Vivaceta are contradicted by period photographs. Since the 2007 fire, the site has awaited reuse; in 2020 the Regional Council approved a project for the Regional Archive of Valparaíso and cultural activities.

The ruin stands in the Puerto district, occupying a whole block between two streets and two passages, a short walk from the port area. It has been in ruins since the Serrano street explosion and fire of 3 February 2007, so it can only be viewed from the street; do not attempt to enter the site.

The 1867 building was erected for General Ramón Herrera on land owned by his wife, where the Hotel de L'Unión had stood. A rival account dating the palace to 1895 and attributing it to architect Fermín Vivaceta is contradicted by period photographs. In October 2020 the Regional Council approved buying the ruin for the Regional Archive of Valparaíso, offices of the Cultural Heritage Service and a deposit of the Natural History Museum.