Hotel Castelar, Art Nouveau hotel building at Avenida de Mayo, Buenos Aires, Argentina

The Hotel Castelar is a 53.5-metre building at the northwest corner of Avenida de Mayo and Avenida 9 de Julio in Montserrat, Buenos Aires. Designed by Italian architect Mario Palanti and built by engineer José Pinzone, it opened in 1929. Because Avenida de Mayo limits building heights, the facade above the seventh floor is set back from the street line, rising to the fourteenth floor.

Designed by Italian architect Mario Palanti and built by engineer José Pinzone, the hotel opened in 1929 as the Hotel Excelsior. Because Avenida de Mayo limits building heights, the facade above the seventh floor steps back from the street line, rising to fourteen levels and 53.5 metres. It took its present name in 1951, when new owners honoured Emilio Castelar, president of the First Spanish Republic.

Federico García Lorca stayed at the hotel during his time in Buenos Aires and regularly met with writers and artists there. This literary connection is still felt today, drawing visitors who are interested in the Spanish-language cultural history of the city.

The hotel stands at the northwest corner of Avenida de Mayo and Avenida 9 de Julio, in the Montserrat section of downtown Buenos Aires. It closed on 9 May 2020 after 90 years of operation, so the building is not open for lodging or visits; it is seen from the street. The García Lorca room was set up as a tribute by the city government in 2003.

In the basement, the peña Signo hosted Norah Lange, Oliverio Girondo and Alfonsina Storni, and honoured García Lorca for the premiere of Bodas de sangre. There, in 1937, Arturo Frondizi and other Radical leaders founded the Movimiento Orientador against Marcelo T. de Alvear's leadership. An anecdote recalls that after a fierce clash between Armando Discépolo and the critic Pablo Suero, the venue was closed.